I hit the level cap a long time before being anywhere close to finishing the game. It's not fun knowing you can no longer advance. And I am never going to use the Illithid skill tree. Shoving parasites into your brain is not something sane characters would do. This is a mature story-driven RPG first, a gamey game far second.
Hitting the level cap wouldn't be so bad if you were strictly on the main quest path. But the game is showering me with side quests which makes the useless XP much more salty. I feel like I should be two levels lower still. The level advancement was just way too fast overall. It's always better to leave the player hungry for more than just sate all appetite.
This is a somewhat tricky balancing act, I'm not sure what the right solution is. IMO they aren't far off, but if you are a completionist, you'll definitely hit level cap early.
In my first playthrough, I basically rushed the main storyline, two companion quests, and a handful of side quests. I left Act I just past lvl5, Act II at lvl7 or 8. It made Act III really difficult and near impossible in some places, but there wasn't enough content I could do to make up for the gap of what I missed in Act I. My current playthrough, I'm doing everything I can, I left Act I and lvl8, Act II at lvl10, some stuff is way too easy and others are still decently challenging. I'll hit 12 likely well before I do the final content, so there will be a waste of exp there.
They shouldn't force you to do everything, especially in the first act, to beat the game and some accommodation needs to be made for people who don't want to spend 20+ hours in Act I. Part of this problem is there isn't enough exp available in Act II to compensate or really give you a lot of choice to skip stuff in Act I. OTOH the side effect of this is that doing everything means you are OP for some of the content, but if they slowed this down too much, I don't think new players would be able to do anything esp. given there is basically 0 catchup you can do in Act II. If they fix this, it would give you more choices to skip stuff in Act I, but would further aggravate the problem of going into Act III too high.
The leveling shouldn't solely cater to people who do everything early in the game, but I do agree coming out of Act I at level 8 seems a bit ridiculous esp when you only really obtain two levels in II and III. I think more opportunities in Act II to gain exp would give you more choice and stuff to skip in Act I and help balance it out some, but ofc if you did all of that (and it wasn't somehow disabled by decision trees), it'd make your problem worse.