I do sympathise, OP. Please don't feel bad. My mother was in her dementia care home for very nearly 8 years and for the last few she was in a most pitiful state, mostly just slumped in a chair, no longer knew me and was incapable of any kind of conversation, or even of any response at all. I did still visit perhaps once a week, but would sometimes miss - she wouldn't be aware anyway, and I knew she was well cared for.
I don't blame you for being angry about the ABs. Having seen so much of dementia (my mother had it for around 15 years and FiL had it too) and after countless hours spent in care homes, I think far too many people are kept alive when so often it'd be far kinder to let Nature take its course.
If they're getting any pleasure out of life that's one thing, but so many are not - I have seen far too much of distress and anxiety that nothing and nobody can relieve - not to mention incontinence and the attendant complete loss of dignity.
More than once in my mother's CH I saw some poor old thing with advanced dementia being badgered and pestered to eat and drink when they no longer wanted to. I know it was done with the best of intentions, but really, WTF is the point?
I made up my mind that I would never allow it with my mother, and thank goodness the question never arose. Plus, by a certain stage of her dementia we had agreed with the CH that except for e.g. another broken hip, anything but palliative care would be verging on cruelty - and as for hospital, drips, etc., hospital is usually a terrible place for anyone with dementia past the early stages - noisy and confusing, especially when they cant possibly understand what's going on, or why they are there.
Presumably it will be largely up to your mother, as next of kin, to be consulted about any future treatment, but some people do want absolutely everything done to keep someone going, no matter how pitiful a state they're in.