I still would take the cabinet out of the equation by using a baffle board (painted like the cabinet to match) and a plate speaker but if you have to stick something in there fill the remaining cavity with old towels or something and make sure the speaker is pushed right up against the grill in the doors (but not touching). I do not think you have to angle the speakers at all. Modern dome tweeters have decent dispersion and treble will bounce right off the ceiling and come right down at you anyway.
This brings up old memories. I was asked to re due the system in an old mansion. In the living room the speakers, AR 3s were stuffed into the upper shelf of a book case with wicker doors over them. I think you can guess how that sounded😜. The wife was determined to repeat history. And I quote, "I am not going to have f--king ugly boxes ruin my room."
So I sold her on a pair of.....Beveridges! 😎