I want to tell my useless siblings I will no longer pick out all the cards and gifts for them since Mom has dementia and cannot do it alone.

One behavior that goes along with what you describe is that your sibs don't thank your Mom for the cards/gifts either, at least not without her asking "Did you get my gift?" If this is the case, here is my suggestion:
Tell your Mom no, explain that her kindnesses would only have true meaning if she were to be able to do it herself. Since she cannot, time to stop that and start a new tradition.
Since this is between you and your Mom, it stops there.
No need to announce or explain to sibs anything. Since they don't visit, nothing will be heard from them either when you just stop doing this.

If ever anyone asks you, just ask them: "You did not know your mother has dementia?"

Just stop, and forgive yourself for wanting to extract some kind of revenge against the useless siblings because you cannot change them. It is understandable and very universal, common to so many caregivers, but YOU deserve better, and you will be the one in the middle to get hurt for trying too hard to make it right.

If your mom enjoys sending them and will fuss about it if you stop then I wouldn't quit, you would be doing it for her sake, not theirs. You needn't put a lot of effort into it though, pick out a variety of cards from the dollar store to keep on hand and let mom pick one of those to send.
If, however, your mom doesn't remember special dates or care much about the tradition there is no point continuing, I gave up sending cards for my mom long ago.

Or, you can continue the tradition for one more year, file the (Cash/money) gifts in a box, and not mail them. Then, when they do visit, retrieve the card, hand it to them. They may start to visit on their birthdays too.
It is all so sad, isn't it? I mean being a useless sibling is sad.

I certainly understand your frustrations! I too, would buy a box of generic cards, which you can get cheaper in a thrift store, or the dollar store, and have them available to your Mom on the kitchen table. Let her do with them as she will, but don't put too much stress on yourself to get them out in any timely manner, Mom doesn't know anymore, and it's not your responsibility to ensure that they get out to undeserving people, who cannot understand that their own Mother is traveling down the road of dementia! Tell siblings that Mom no longer has the capacity to do gifts and cards anymore, and that they need to come to grips with it! Maybe one of them could step up and help a little, this is an awful lot to manage, all by yourself! My heart goes out to you!

I went through this for the first 4-5 years I was here. Mom wanted to send everyone a card on their birthday and to buy presents. Of course, it was me going out to shop for the presents and cards. After a couple of years she couldn't remember when the birthdays were, so depended on me to remember. I didn't know when the birthdays were and sometimes I would forget one of the grandchildren's birthday. Now the kicker was that none of these people ever sent me a card except one brother. Also, the cards meant nothing to them -- I knew them well enough to know that. So why was I buying and sending things to 15 people who didn't care one way or the other? There was zero quid pro quo happening. Finally I told my mother why didn't we just cut it down to my brothers and their wives. She agreed.

Wow! Great answers to all of you! Yes, the cycle must be broken and if she feels the dire need around Christmas, I have LOTS of generic ones of those! They do not ever acknowledge when she (me) sends them cards with gifts. I will tell them when they show up on Christmas that I am no longer going to pick out the gifts and cards for them. For God's sake, she is 80 with dementia, isn't it time to stop expecting and actually do something for her for a change?

Yes Rainey, all traditions unreciprocated should expire at age 65, imo.

Thank you, Rainey. Thank you thank you thank you. Now I know it is not just me.

I last bought the younger of my brothers a birthday card in 2014. My mother had a horror of giving money, it always had to be a proper present; but by then the only time I had for shopping was my four hours' respite care once a week, and we lived half an hour from the town. So off I went, bought a gift voucher, got home, got mother to sign the card, stamped and addressed it, flew to the post box, flew back again and thought "phew! Mission accomplished." That was over half my time out for that week gone.

Not a word of thanks, not a phone call to me or his mother, nothing. I tell you, from then on I felt not a twinge of conscience about dropping the whole dam' charade.

Churchmouse,
My mother too felt obligated to give 100 dollars for every occasion. I finally had to break the news to her she was NOT a Baroness of a royal family and could not keep giving her limited income away. Since I have POA, I had to take away her checkbook and credit cards. That did not stop her from everytime we were at the drugstore, "Oh, we need to get a card for ..............., it's their anniversary, it's Thanksgiving, it's Valentine's Day, it seemed every damn month it was something. I started feeling hostile because then I had to stand there trying to find the appropriate card, where is the dysfunctional family section cards? Can't get the ones saying how wonderful and thoughtful they are and all that crap!!! I just dread the damn things. I told Mom not to get me any, I know how she feels about me, I don't need Hallmark for that validation. All she gets from my brothers is cheap candy or some plastic trinket, like she needs one more damn thing, and nothing that really speaks to her personality. I feel like saying, "Do you know her at all?" Here Mom, here are some nice cheap scented candles even though you sent a hundred dollars. They just disgust me. I do not consider them MY family, hell, strangers have shown more compassion! You are not alone Churchmouse, Iam done playing the game so they can pretend everything is hunky dorey.

Oh gosh yes! The polyester satin blouse, two sizes too large, in a dizzying navy and fuchsia print - ! With the 'marked down' price label still attached as a chaser!

My mother used to send Happy Anniversary cards to my ex and his wife. Though to be fair, Wife II was more thoughtful and affectionate towards her than my siblings were.

Mom has always given money to my elder siblings and and her grandkids for xmas and birthdays and like everyone else it fell to me to buy and arrange - of course nine of them helped mom get me a card

So now my plan is to find the cheapest cards I can and fill them with mom's currency which since her move to memory care is authentic looking play money 💵

Churchmouse,
Thanks for the laugh!!!!! Sounds about right though. We are not alone in the insanity :)

Rainey, I gotta say, I like your style. I'm the only one for my folks and get stuck with the whole card mess for a slew of grandkids. I have to get the cards and the money holders and sit with mom and sweat out how much each kid should get and then mail or hand deliver them all. I understand your frustration. F...... Hallmark!

At one time I bought my Mom a package of cards from Hallmark [no more boxes of cards like they had in the past].... I thought the package of cards would save me from running to Hallmark, but it didn't.

Mom wanted cards that said "Godchild" [not that easy to find anymore] even though the oldest Godchild was in his 70's, the rest were also senior citizens. But I didn't mind as these 3 Godchildren always remembered my parents with frequent telephone calls and with greeting cards. As for gifts, I think my parents wrote out checks to them.

I know I have reach senior citizen status when gifts from much younger people to me are oven mitts and kitchen towels [I don't cook]. Hand lotion vanilla scent [which I dislike]. And oh joy, just what I want linen hand towels [can't wait to get the iron out] :P One can drop hints but no one pays attention.

Growing up on a farm outside small community made it difficult to go to the card store very often so we always kept a selection of birthday, anniversary and sympathy cards on hand and a box of gift wrap suitable for every occasion. I must have packed those things up when we moved from mom's, hmmm, I wonder where they could be?

cwille, I have my own Hallmark file cabinet filled with cards for all occasions. While going through the cards the other day, I found a Hallmark get well card that was 35 cents full price, now that is going waaaay back. I also have the folded gift wrap paper, back when the paper was heavy enough to use as wallpaper, todays wrapping paper is so very thin.

All your stories have brought smiles to my face and laughter! It is sad it ends up being one of us that this ridiculous chore falls upon us but this year, I wil let them know that "I" am no longer getting them their stupid cards and gifts so suck it up and be an adult for once!

Well, here we go again, in dementia land where she doesn't remember, it's coming up on Thanksgiving and then of course, the ever popular Christmas. She has already started the card shopping request. I feel like such an Ogre telling her, "Mom, we already talked about no more cards!" She doesn't remember so many important things but she never forgets those damn cards!! Pray for sanity over the holidays.