Tauriel is sad because she has reached her 10th level of Fighter and she can't go higher.
It seems to me that Level Limits are an awful way to balance races. Yeah, yeah, some will cynically say that there's no such thing as real game balance. It's an argument I will never give credit to since old-school classes need different amounts of XP to level up depending on how awesome they are, so moving on.
With all due respect for the people who made D&D into what it is today, I just HATE Level Limits and know for a fact that countless people ignored them even when they were a thing. At no point will it ever manage to actually balance out characters or make the game fun for anyone. Let's say you're an Elf in a game with Level Limits. You are more awesome than your Human friend. During your first levels together, you are always at an advantage. And then one day, suddenly you stop leveling. For a few levels it's all good, but then you realize you have nowhere else to go while your Human friend just keeps on going up those levels. You started off being a bit better and now you're obsolete.
I imagine someone could bring the argument that in old-school games it takes a long time for things to get there. Well in that case, if you're not gonna get there before months or years of real-time play, how is playing a Human worth it during all that time? And what's the point of having played an Elf for all that time only to watch your character at some point become useless?
I prefer the way taken by Castles & Crusades and Basic Fantasy Role-Playing where there are no level limits. Humans get an advantage too and that advantage is either a bonus to your rolls or a XP bonus respectively, not the ability to limit every other player race just by existing and not being as cool while feeling a desperate need to remain relevant to your campaign setting.