I almost completely agree with your review of "Oppenheimer." I didn't enjoy the movie either. The movie got a lot of hype when it was out, and since the time of your review, the movie has gone on to win several Academy Awards, including Best Picture. So, we're apparently in the minority.
I had two big problems that really hurt the movie for me. It was three whole hours long but felt like five or six. I think the addition of the trial storyline both added too much material to cover and also necessitated the non-linear structure which might not have been needed otherwise. If the movie had covered just the production of the bomb and the aftermath of its use, maybe that would have made for a leaner, more concise movie.
The other issue was Nolan's insistence on having the music too loud during informative dialogue. This is the type of movie that doesn't need to be super entertaining. It's a docudrama, so it should be more educational. There were several moments where I felt I was about to be explained something important and informative, but then I couldn't hear it for the music being too loud. What's the point of actors rehearsing their lines, setting up the shots, directing the actors to emote as they deliver, and then pick the right shots for the edit, just to plow over the dialogue with overly loud music? And, it's not just an issue of the theater I attended. Nolan made a similar choice in the movie "Interstellar," and at least one reviewer I watch on YouTube commented on the same issue being in "Oppenheimer."
The only part of your review I disagree with is the use of the word "incompetent." I don't think Nolan doesn't know what he's doing. He clearly made a movie that appealed to most people, both the general public and voting members of the Academy. Even I could "feel" the movie potentially winning awards as I was watching it, despite not ultimately liking it. I think Nolan is more than competent when it comes to raw filmmaking talent. But, he does sometimes make some confounding creative decisions that can shut out a portion of the audience. This time, you and I were on the wrong side of some of those decisions.