5E is a big problem because it is a very dumbed down version of D&D with hardly any options in it. So when Larian removes every "non D&D" part of the combat it will result in a very boring game.
Whats more, they have reduced how high a bonus can go (bounded accuracy), but kept the D20. This leads to RNG being the main factor which decides if you succeed or not. No matter how much you push a stat or dump it, in the end mainly the D20 matters while all your choices only having a minimal influence.
So there is really no way to play a peaceful negotiator and an intimidating brute, etc. because it is not your character design which influences what happens in the game.

So yeah, 5E is the big problem of the game because with its extremely simple design it holds it back.

The other big problem I see is on Larian, namely the Origin system. Or rather that the game basically expects you to play as one of the DMPCs to get all their quests and stories. If you dare to make your own character you won't get anything to compensate you though and only have the bare minimum of story about yourself.