It’s an interesting “what if” thought exercise. What if the nu-Trek shows had copied The Cage/WNMHGB for uniforms (so we don’t deal with the “minefield” of micro-mini skirts and beehive hairdos) and the ship/set design from the rest of TOS/TOS-R from the start? I’m not entirely convinced the majority of people would reject it. Trekkies or casuals. But I don’t know for sure. Maybe they would.
On the whole I think Trek fans would accept the look because “of course, it’s a TOS prequel. That’s what the ships and uniforms are supposed to look like.” Would there be some Trekkies turned off, of course. But I don’t think there would be arguments saying “they should have updated the look”.
How much of the casual audience would really be turned off by simplistic looking sets and costumes? That’s tough to say in part because we don’t know how much of a casual audience Trek pulls in.
As an aside, it’s funny, until people began defending Discovery I had never heard people say “Relics”, “Trials…” and the Mirror 2-parter from Enterprise “didn’t count” because they were just “love letters” to the fans or whatever. They were just accepted.