I enjoy the leveling up aspect of games, although grinding can be tedious (though not every RPG requires grinding to be strong enough to take on the enemies you need to face).
I've tried to find out exactly what constitutes an RPG, but there seems to be arguments about what defining characteristics there are. Most seem to think levelling up is a defining trait, though. Technically speaking, any game where you play as a character would be an RPG, because you're taking on the role of said character, but nobody would say Call of Duty is an RPG or Uncharted or anything like that.
If I think the levelling up in a game is so tedious that it ruins the experience for me, I just won't play it. Usually, though, I enjoy levelling up. I think turn-based RPGs wouldn't be as fun without levelling up. Growing and becoming stronger as you progress through the story is part of the appeal for me, especially in the kinda games where you can sorta decide how you grow. Like, in Pokemon, you can choose the moves your Pokemon learn and you can focus on some stats more than others. I enjoy that.