The last MH I played was MH Ultimate 3 Ultimate on Wii U. How much different or improved is XX/Generations?
4 brought a lot of improvements to the series that carry over to Gen, so the experience is much improved. They also added all of those special "fighting arts" but they also give you an optional art that is the same old regular play.
Conversely, I've dumped a lot of hours into Monster Hunter: Worlds, so while i'd love to play a monster hunter game on the switch, i'm not sure I want to roll back some of the improvements made in that game.
I've not delved deep into MHW, but from the sounds of things the improvements are not so steep that you couldn't play without them, but that is a YMMV situation. Some people can't go back to non-HD, I struggle with the PS1-era graphics, others can't play low FPS.
But at least there is a demo of this game on the Japanese eShop, and I'm sure it will be making its way to the western eShops as well, so you can give it a whirl and confirm your suspicions.