The graphic design is for a UI: It's already on OUR side of the 4th wall. It's NOT a part of the fantasy adventure - it's our personal interface for interacting with the fantasy adventure. It's most idea situation is to be unnoticeable and practically invisible to our subconscious as we use it. A clear, clear but otherwise nondescript UI is one (not the only, but one) way of achieving that invisibility. But regardless, this is an aesthetic complaint.
Let's be honest though - Solasta's UI doesn't look pretty, it sticks out like a sore thumb, and draws attention to itself in the all worst ways possible. It is aesthetic complaint - all it needs is an artist to spend a decent amount of time to make it look good, and buttons nice to click. Not problem with design, but budget spent on it.
I have no problem with how BG3 UI looks - just what funcionality it offers.