It is very true that many groups are falling apart; possibly the majority depending on how you define "falling apart".
Of the groups I am familiar with, one which is working well is one around a C152 where one man is in charge of all admin stuff, and the other members (about 25 of them!) get obviously very cheap flying. They lease the plane in so no cost suprises. They used to own a C150 and that worked well too because with 25 members money was not a problem. Their Annual costs were eye watering, about 2x to 3x what I pay on my TB20, but with 25 members who cares? But that group works because they have a niche: very cheap flying, and everybody knows they cannot do any more than a little bimble, not too far away. A lot of pilots are happy with that.
If you want to have 2-week holidays with the plane, you need a very small group made up of understanding people.
One other group I know that's working well is 2 people around an IFR plane. Both have enough money and do similar flying. Such groups are very hard to set up though because finding people with money and competence and the desire for full IFR capability is very hard. Almost everybody with an IR already owns his own plane; it's a bit pointless doing an IR if you cannot afford to buy a plane afterwards.
However, a group is simply the best option for somebody who cannot afford to buy 100%.
Renting is a very poor option; you either fly junk, or you pay loads of money per hour which is a disincentive to currency and usually means no long trips away.