Transmog should be a core aspect of any game, imo. Our characters should look like who they are, not just whatever piece of armour has the best stats for their build.
Well... I disagree. Role-play and build ideally should be one and the same. While, I of course, theoretically dont mind an optional transmog, ideally I would want the look of my character to represent systemic roleplaying choices I made (including build). So it's less that I have an issue with transmog but if, there is discrepency between system build choices and the game represents the character visually, as you suggested in:
Our characters should look like who they are, not just whatever piece of armour has the best stats for their build.
than that is IMO a bigger issue, than lack of transmog.
And BG3 is forgiving enough, that you can wear whatever you like, for your character to wear and stilldo just fine.