The YHA is at something of a crux. Many "iconic" properties are old and falling apart, and need huge sums to renovate them that YHA don't have.
On the other hand, customers don't want dorm accommodation as much as before - they prefer family rooms, with en suite if possible. That's doable - what is less doable is modifying old properties with large rooms into new interiors with smaller rooms and more modern facilities.
Coupled with that, they have apparently had money problems and an awful booking system that meant no one point - booking direct with the hostel, using central booking or booking online - had any idea if the hostel has vacancies or not. Fortunately, this seems to be on the way to being fixed.
YHA hasn't been for "youths" for decades - but they do have users and supporters, and are probably now in better shape than they have been for a decade. In conjunction with Independent hostels, there is still a half-decent network - which is good for walkers of all ages!