OM(F)G, this thread fills me with dread. I certainly hope that BG3 will not turn out to be fan service for waifu-worshipping incels. The way romances are currently handled in EA is not great, which adds to the fear.
That being said, Minthara could be made into a fine party member for evil MCs. But there already is a cleric that seems compatible with all kinds of good/neutral/evil playthroughs. Maybe joining the Absolute (if that kind of play-through/choice is possible) will alienate almost all party members (except Astarion, maybe?) and Minthara will replace Shadowheart in that case...
You speak as if having a waifu is something bad.
If a player has a desire to waifu-worshiping, then the game designer and writer have done an excellent job, and the players really like the character.
I agree that more attention needs to be paid to personality, character quests, decisions, various joint adventures, emotional aspects of relationships, a possible arc of redemption and much more, it shouldn't be just about sex and kinks. But it should be too.