Oh I agree that leaving it at that is in fact rather bad from a writing perspective for a character whose purpose in the Inquisition is as one who seeks growth and to find her place in the world.
I feel it would be fair to argue this is one more notch in the belt that is trying to bring the Dalish down more and more (I enjoyed some things about the Dalish in Inquisition, but others just felt unnecessary). The lack of growth for Sera is in fact a very bad part of the romance arc, and it's something that does need to be addressed.
But trying to force Sera to change isn't going to work. Sera needs to come to you and work through these things. She needs to start it. So in the end, the lack of follow-up is bad from a writing perspective -- that much I agree on. But I don't think that such a follow-up can ever begin by the Dalish Inq. going "Hey Sera, we need to talk about your beliefs" because that will cause Sera to shut down.
I suppose one could use headcanon to do such things, but headcanon being used to fix problematic writing is something that I abhor because it makes the writers seem lazy and while it makes the players better writers in the end, it's still.... something I dislike.
Especially if it's just not gonna matter anyway.