You can tell that the people moaning about QTE's are either trolling or haven't played Monster Hunter before. The mounting works exactly the same as MH4 and MHGen, except you now also have a charge attack for it too.
Well it does seem like they added some mechanic where you have to jump to a different part of the monster at certain points, which does seem to be a QTE. I don't see why anyone would complain about this though... Expanding the simple mounting minigame is a good idea since the current one can be done with your eyes closed.