I was only in “passable” bands but being in a band is like dating every member at once. Add in the pain of touring and that can get ugly fast.
Swap out some members and the fit may be different and not marketable.
But you are right, once it starts to feed you well you move your focus to meeting market demand or if you follow your personal interests you risk alienation of your fan-base.
I will say that people who are independent song writers or don’t hit it big can last for much longer. Tom waits comes to mind.
Some become great producers and/or song writers.
Some just make loads of great music for decades in relative obscurity like Skerik.