I disagree with everything you've said, and I think that you're looking for something to be offended by. Here is why I think that you are incorrect.
Karlach:
Karlach actually does have good endings to her storyline. If Karlach becomes a mind flayer, she survives. Or if you complete Wyll's questline they go to Avernus together and it is suggested that they eventually fix her engine.
Wyll: This is the one I disagree with the most, because -
1. Wyll only became a warlock because he was forced to, he was given a choice between selling his soul or letting dragon cultists destroy the city. He was NOT "lazy" as you put it. 2. If you complete Wyll's questline and break his contract, he becomes a ranger and fights demons in Avernus, This clearly shows that he was a capable fighter all along and would've been fine without warlock powers.
Minthara:
While I agree MInthara should have more content and a proper questline, I don't agree with your reason why. I think the reason is that Minthara is initially an enemy, and only joins the party in Act 2, so will naturally have less content, and also recruiting her requires either siding with the goblins or meta gaming and knocking her out.
Laezel: It is very well established DnD lore that this is how githyanki are. The writers are just portraying the lore accurately.
Tieflings: Where do Larian's writers tell you that refugees are bad? On the contrary, you get penalized quite harshly for not helping the tieflings, as you lose access to merchants and allies later on. As for the part about them being victimized, I'd like to point out that this is also true of the Gondians, and I don't see you complaining about them. I don't see what is the issue here.
