For me, it's all about dynamics and flow. Smacking into rocks and roots oofing your way down something super steep isn't much fun tbh, but I do like some challenging trail obstacles. But it must be said, better if there is some speed involved.
Pushing yourself on fast trails means going faster – on uber slow tricky stuff it just descends into trials.
I think a lot of the people who slag off trail centres etc on here don't have the minerals (or skill) to take them fast enough, to be honest. Those trails you have to work with to get them to give up their wonderous secrets.. they don't just hand it out on a plate.