Does the OP's question mean a course that is newly created, or a course that is new to me?
If the former then the biggest unforgivable is course layout. I hate courses that are completely on top of themselves. Tee boxes inches away from greens, shared fairways, cross-over holes. Hate hate hate. I also dislike courses where the tee boxes are another full hole away from the last green (so many resort courses, especially overseas - where you have to weave thru the back alleys of housing estates to get to the next hole). There's a definite Goldilocks distance where the each hole is just close enough, and just far enough at the same time.
If the latter, then it's courses that are up themselves. I don't care how many majors you've held. And I also don't care what your members have voted for. If you think that telling other adults, who are smartly dressed in the modern world, how to dress then you don't deserve my custom.