I upgraded mine to an S23 last March. Main reason was because the battery could no longer last through the day. Otherwise I was perfectly content with it.
I like to buy the phone outright rather than get one on contract but the flagship phones are just so expensive nowadays. My S8's battery is getting steadily worse so I'll probably upgrade when I can no longer ignore it. At the minute I just don't feel like I can justify such a massive expense for something that will essentially just be more of the same only a bit bigger and a bit faster. Maybe I'll go for a Pixel instead.