I too was disappointed with "Glass Onion: A Knives Out Mystery."
My first struggle with the movie is that it breaks the first rule of a good mystery story in that you need the audience to have enough information that they can plausibly solve the crime themselves. Glass Onion only provides information when it becomes relevant to move the plot along. You could have never known certain things, you could have never even guessed at them because the information did not exist right up until it was needed in the story.This happens repeatedly. Midway through there is a plot twist that you could have never guessed or seen coming and that pretty much ends any sense of suspense or intrigue.
I also don't care about any of the people in the story as people or characters nor do I find any of their relationships convincing. It seems implausible that any of them would have ever been friends. Close your eyes and imagine these people hanging out at a bar together and you can't. How did they interact? What was their friendship like? You never see it and so the weight of the strain of the existing relationship isn't ever fully felt. The characters in a "Knives Out" were caricatures too, but they were family, not friends. Everyone knows that strain. Everyone can relate to that relationship dynamic. You don't get to choose family. Friends tend to match each other to some extent. Give them some kind of connection. They are all trivia nerds and were a trivia team. Anything.
With all that said, I want to rewatch "Glass Onion: A Knives Out Mystery." I want to see how much was visible in scene. How much could I have technically figured out. It is an interesting movie, I am just not sure it is a very good one.