BB got boring because the dev doesn't know how to advance the story. Eric was just a plot trick to stall the advancement with the girls.
Devs should learn from sts how to make an incest game interesting and not be afraid of sex and losing patreons.
I play these games for the seduction of the hot girls, not for some Eric (that's pretty gay IMHO).
The incest part is the ultimate taboo, the biggest challenge you have to overcome, there's no need for other men as rivals, and if there are, like in this game, the hero, the mc, has to be able to win, otherwise it becomes frustrating, and unless you're into masochism you don't want that.
If there's other alpha man than you you become his bitch too, sort of.
These games are about role playing; you play as the mc, be it a douche or not. If you played in a third view these things wouldn't matter, since you're just an spectator, but in a first person view (which is the reason to play a game and not watch a movie) the fact that ther's a guy fucking all the girls makes you a cuck, lato sensu.
Oh, in an incest game, formally, not related girl is for you, hence the taboo, but since it's an incest, especially the girls in the family are your love interest, otherwise it wouldn't be an incest game.