I said that 5e is "fine". And it really is. It's good even. I do have issues with it, however.
1e and 2e, honestly, felt very blah. Gaining levels through level 8 felt very powerful, especially for multiclass characters, but realistically it felt like diminishing returns set in pretty quickly since all you really got were nonweapon proficiencies, better attack and save bonuses, more HP, and, if you were lucky, better skills or spells. It didn't feel bad to gain levels, but you didn't really know any better, either, and since it was so easy to lose levels, you didn't (or we didn't) so much measure yourself against them.
In 3.x and Pathfinder (even PF2 from what it looks like) it doesn't feel to me like you've got a complete character until about level 8. And that's way too late because the campaign is half over by then. You're still picking up basic features until then, and if you're interested in a prestige class, you often never felt like your character had started until you reached a given PrC level and picked up that core ability you were lacking. It's one of the things I grew to dislike about 3.x. It felt very viscerally enjoyable to dig through 5 different books for the perfect abilities and classes in 3.x, but that feeling didn't really translate well into gameplay. 3.x felt like it had a very good minigame for building a character, but that what it lacked was a good system for making that character feel like it was complete or whole during play. For PF2, I think what really kills it for me is the fact that Ancestry (i.e., Racial) and Skill abilities are gained as you progress in levels. To me, it looks like level 1 in PF2 is a paper doll with perhaps 4 abilities. I don't know. The whole system for PF2 just turns me off in a very straightforward way.
In 5e, to me, you feel very weak levels 1 and 2, but they're short. Then every character feels established by level 3, and feels like an experienced character by level 5. By level 8 you feel quite heroic. By level 11, you feel like a powerful veteran. Most characters will have a 20 in their primary stat by this point. I absolutely love character progression through level 11. It is as close to perfect as it's ever been. However, level 11 is what I consider the end of real character development. I say that because, for essentially all classes, levels 12, 13, 14, 15, 16, and 17 feel completely dead. Those levels are just a slog. For just about every class (and certainly for every class I've played) there is no ability that feels worthwhile at those six levels -- with the obvious exception of new spell levels and possibly Slippery Mind (Rogue) and Diamond Body (Monk). Maybe they're just trying to put a plateau in the middle of the game before 9th level spells, but in my experience it just lasts too long, and I'd frankly be fine with 9th level spells showing up after the "end" of the traditional game. They kind of always have anyways. Level 3 you feel like the class you selected, level 5 you feel experienced, level 11 you feel like a powerful veteran. And then nothing changes until level 18. Even your attack bonus or spell DC doesn't improve much compared to the first half of the game. It should be +5 at level 1, up to +9 at level 11, and then to +11 at level 20?
Beginning with level 12, it feels to me like nobody gets anything interesting (beyond new spell levels) until you hit level 18. Most classes just have "Hey, you know that thing you do sometimes? It's trivially better now or you can do it once more per rest!" and they stick that on the class table and say it's not a dead level. Yeah, that's still a dead level. Every time I see an ability like that I think, "The Rogue doesn't have +1d6 as their class ability every other level, and that's a better new ability than I'm getting right now. The Rogue gets a new ability *and* his existing ability improves." Maybe it's because I played a Rogue first. It just doesn't feel good to advance your character beginning about level 12 and lasting until you get to the capstone levels (18+).
Speaking of capstone levels, I would much rather take all those interesting and game-changing abilities that classes currently get at levels 18, 19, and 20 and move them to levels 13, 14, and 15. Then, get rid of all the chaff they give you at those levels currently, and for levels 16 through 20 just give every class an Ability Score Increase every level. Or, heck, have two ASIs per level. Just stop putting fun and interesting things at endgame levels because nobody gets to play with them. They're all carrots that nobody ever gets to, and even when you do manage to get to them, you only have them for like for six weeks after playing a year and a half. Just give us the carrots and make the end of the game just actual diminishing returns. Advancement stops at level 20 because you've reached the pinnacle of mortal advancement, and it tapers off well before then. And that's completely fine to me. Levels 16 to 20 are almost always about wrapping up the campaign or doing a fifth season of Babylon 5 because the players don't want to quit.