I loved Legion. But that...
...ending? Oof.time travel reset, none of it happened
That's one way of looking at it. I think of it as David giving himself a clean slate and a chance to be better, free of his curse. Or did any of it happen anyway? Either way, it's very much a journey rather than a destination show, and it's brevity is to it's advantage too. 5 or 6 seasons of it would be too much, but 3 feels like a nice number. It doesn't outstay it's welcome and gets out while it's still good.
And if you watch the show on, say, Hulu you can see how good it looks in HD. Infuriating...