I don’t think most people are sick of them, I think most people don’t care one way or another about them because they’re getting on with their own lives. Most people stopped obsessing about famous people in their teen years, if they ever did.
Having ventured onto this board occasionally though, I can see how people would think everyone is sick of them. There are people that seem to spend a big part of their life posting their dislike about everything they do. A small but very vocal minority. You only need to spend 30 minutes here to get a feel for the dislike on this board for them. I have seen threads about Harry and Meghan on AIBU and it’s much more balanced and most people don’t seem to care but do think some people are obsessed with them. You have to pity anyone that spends so much time writing about a couple they don’t know. When I don’t like someone, I might make an occasional comment, but these people post weekly or even multiple times a day. I think they’re lonely and have found ‘friends’ who all egg each other on to keep going on and on about Oprah, Netflix shows, jam, over and over. I think spending so much time on any one thing isn’t really healthy.