Broken questlines (anything to do with mol)
Broken dialogue that doesn't account for player choice in previous dialogue. Characters will forget that you're not supposed to know something and then speak to you like you made that choice
poor ai pathfinding, the group movement around the world in general is extremely finicky and outright bad in areas with hazards, jumping between platforms of different heights
Heavy savescum nature of a game. Many bullshit moments you can't predict, combat encounters you couldn't have known you were under leveled for. In dailogue, I will never accept a failed roll on a level 5 or lower requirement, especially when the requirement is one of my affinities
waukeens rest is another example of poorly designed quest parameters for a notable location, invisible timer that can be triggered from the main road with laughably bad context clues to let the player know they are being timed for something and they need to change the focus of their attention to the new thing or lose out on the questline entirely
several time sensitive quests that do a bad job in general of letting you know they are timed and can lock you out of content without a fair warning (waukeens, following harpers to moonrise, Grymforge, submarine in act3)
entirety of act 2 was bad. Act 1 was fine, act 3 was the best (although missing half of the games namesake city you spend all game hyping up), but act 2 was just shit. Storming moonrise and some of shars temple are the only highlights
camera sucks for an any indoor enivornment/fight. The fight in the ghost mansion is the pinnacle of this.
Wonky facial expressions in cutscenes, most of that stuff is done right and the voice acting is great but there are many of scenes where your character or a party member makes an inappropriate, ME: Andromeda tier face.
5e system is overall a downgrade from DoS2 minimum stat requirement system for saves and checks
No harem option