They're not my favourite thing but I can see their place. Good for a quick outing without having to look for anything. Only been to three (Sherwood, Dalby, Grizedale).
I would say the nicer setup is at Grizedale of the three.
Dalby is nice, just wonder off or skip the bits you don't want. Some stupid 'made' bits but you can skip them.
Sherwood I only know what we where shown but looks a nice forest to explore with some bits of Trail to play on.
The bits I don't like. Long sections of Board. Why! That aint natural.
The fashion for Bloody Berms, does my head in, I like the skill of trying to do a corner properly and they get in the way.
All are great with the Family though. Everything you could want is there with young ones as the easier sections are quite well maintained and of course miles from traffic. Of course it can often be found just down the road if you knew it was there. But it's a nice day out.
So if they maintained wooded routes, stopped using fake stuff to build them and move sections to let bit recover all would be good. and at £7 for parking there, the double priced food etc, then it should easily pay for itself