The YHA “board” (trustees) are nominated and elected by the members. I wonder if any of the people who are so disgruntled with the YHA have got involved e.g. attending the AGM etc. Or do you want to treat it like a “commercial” hotel chain, in which case if that is what it seems to be evolving into it is perhaps no surprise!
Personally I’ve only used SYHA properties not YHA ones and generally had good experiences. There’s definitely been a culture shift since the 1990’s but generally IMHO that is positive. Perhaps there is less requirement for a collective body and the internet (as a way of communicating the existence, availability/booking etc) for independent hostels/bunk houses – whereas 20 yrs ago the “hostel book” was the starting point.
It would be tricky to pick a specific hostel as being the best. What would the grounds be? At both extremes luxury/comfort could produce a great hostel, but simplicity/basics could be just as good. And a brilliant hostel in a poor location would be worse than an average hostel in an amazing spot.