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.