I mean to be fair, it's still a fine ending, we just don't want it to be the ONLY ending. They can absolutely keep the "gang goes to Avernus" ending without compromising the ability to one day fix her engine.
It's not "the gang goes to Avernus" though. It's Karlach and Wyll (if you made specific choices in his story) go to Avernus, and Tav, but only if Tav romanced Karlach.
That ending is also not available if you are playing Karlach as an origin character (you can't take anyone with you to Avernus in that scenario).
If you play as Karlach, there is a scene where the entire party joins you to Avernus? I haven't played as Karlach.
