Do we pull and fill cavities or leave the man in peace?

I agree with the Doctor. If there is no infection--you would likely smell it--- let him be. Most dental insurance won't cover monthly cleaning, but they would cover it every 3 months.
If you pull teeth, you have to be very vigilant for proper healing and at his age that takes a long time. As far as filling, there may not be enough tooth structure left to support the filling. You may create more problems than you solve.

" monthly cleaning "
that sounds like a dentist . ive often thought of offering them weekly sidewalk checkups for 150 bucks a week .

eh , whatta i know ?
ill go back to jamming with doro . we seem to be on a common wavelength .

Forget the water pik unless you plan to use the water pik on Dad yourself. When one becomes elderly, they just want to use a regular toothbrush, some good tasting toothpaste, and nothing more.

My Dad [94] had one of those water piks and while cleaning out my parents house once they had left the house, there sat the water pik all moldy... gross. So I threw it out. Dad wanted a new one so I bought him one months ago... and right now it has set empty on the bathroom counter yet to be used.

Personally, if this was my Dad who needed teeth pulled and cavities filled, I would have at least the cavities filled as they will get deeper and start to hurt. Next would be a root canal which isn't easy.

If you leave rotting teeth unattended for too long, the cavity will worsen as mentioned here. Don't let this happen because it can lead to problems later on such as pain and infection, and infection can spread to the brain and actually kill you. I would get this addressed soon as possible so that no problems will develop later. There may not be any problems now, but you don't know they won't develop later because they probably will