Let's level set. Compared to what, Pathfinder sucks as far as characters? BG3? Solasta? DOS 2? Original BG games?
In terms of most cRPGs I've played, I think both Pathfinder games have hit par at least in terms of side characters. I mean, sure, they don't have a ton of depth, but they aren't just storyless nobodies either.
So what are we comparing them to?
Well, it's hard to judge BG3's ones yet, but apart from Astarion (personal distaste), I found them all well-enough done. They deliver their personalities and quirks across without slapping the player in their face with a blatant "I AM LIKE THIS BECAUSE OF THIS AND THIS" exposition dump. Them all being awful jerks is more of a meme that I never understood, myself.
Original BG games: 1 barely has companions as characters at all, but that actually allows to carry even the ones like Xzar and Xan and, I dunno, Shar-Teel around without them growing really annoying to be around. They are mostly all one-note, but that one-noteness is well-integrated into how they work. Whereas in 2 - again, I can't really find a cause to complain about most of them, and the romance storylines really make Viconia/Aerie/Jaheira's personalities stand out in a way that doesn't feel forced. I suppose Anomen is an utter dunce who is, for the most part, stupid to a very grating degree even after he starts to know better (they didn't really readjust him for after his personal quest), and having female characters be restricted to him is very unfortunate, but that's about the only complaint I have with them. That doesn't quite extend to the EE ones, though. I can see what they were going with Neera, but it just doesn't land. Dorn being devolved into wanting to make the male Bhaalspawn his gimp was... a revelation, and his quest just goes nowhere unless you do it the "intended" way. Hexxat feels like she was thrown in just so she's there, and is very awkward to use (a mechanical complaint, but still). And Rasaad is... what was his deal again?
Does Solasta even have memorable characters, by the way?
Anyhow, my complaints are mostly due to my personal distaste for Owlcat's writing. Their humour doesn't really amuse me (the whole Inconsequential Debates moment in Kingmaker was unbearable), their camp banter is uninspired (let's have a prick joke #9!... that isn't even funny. Or have them waxing philosophical in a very pretentious manner) or overwritten (Linzi...), their way of exposing characters feels like they are reading their own biographies at you in the most annoying way possible. Part of it is how Owlcat's writers structure their dialogue lines and text in general (I mentioned before that it has Russian writing style all over it with barely any effort made to adapt it), and the other part is just awkward their texts feel to read in general. I could tear something like PS:T letter by letter reading between the lines, or would find the PoE lore dumps enjoyable, but theirs are just... flat and unmemorable?
And before I am called a Larian fanboy, I'd like to say that I don't think their characters/companions are the best thing ever or even if they are super good or anything. They are certainly the best Larian have ever pulled off (Lae'zel might be the coolest companion they've made, and a worthy successor to Dak'kon and Zhjaeve as a gith party member), and a marked improvement over their two previous games (although I still think that their best sidekick ever was the Death Knight from Beyond Divinity), but Kana-Eder-Durance from PoE1, the PS:T cast, and NWN2's companions (MotB's in particular, although Ammon Jerro is fantastic as well, and I have an apparently really rare fondness for Casavir. Their arguments actually feel lively and witty, rather than Owlcat's phallometry contests (not literally - not always - but still, the comparison stands)) still remain my personal favourites. DA2's were fine too, apart from the butchered Anders. I'll give Owlcat one point in that their characters are markedly better than late (ME3 and onward) Bioware's. And they are not as flat as something like Sword Coast: Legends. But that's about all the praise I have, save for what I had mentioned in the last post.