My first YHA experience was in a school party of 10yr olds (led by a scoutmaster, it was a prep school with its own scout troop) going round the IoWight. Lots of chores making the sandwiches. It didn't really switch me on to hostelling, I preferred camping (only to be expected when you're only 10, camping seemed so much more fun).
In the early 70's I joined the junior section of the local YHA group in Cheltenham and that was what got me into cycle-touring (and also club cycling and, much too briefly, TTing).
In 2009 I brought a small group over to N Wales from my french club, intending to use hostels to keep the price reasonable. It was at that stage that I learnt how much the hostelling scene had changed. Our mix ended up with three hostels (Liverpool, Llanberis and Chester), one pub b and b (Prestatyn) and one independant hostel (Bala). The closest we got to the hostel atmosphere that I remembered from my youth was at Bala!
I have never stayed in a youth hostel in France or even researched the idea. I did a FFCT training course at one in Brive but it didn't seem to have much in common with the YHA. I think the FAJ hostels are probably a bit far apart and probably car-orientated as well. Camping is so much more accessible and more fun as well.