Good point. I think it's worth it to make sequels if you're adapting a good novel and you want to include as much as possible. But the superhero phenomenon to me is just a soap opera with muscles and costumes. Like Star Wars is a soap opera with different elements. It's designed never to end, and in the end it becomes as him drum as the next episode of a mediocre TV show. You hire some asshole or group of assholes to churn out new "content," cut that to its most generic elements, include the worst writing mechanics like plot holes and pointless tangents, and now you have a film. I see this phenomenon like the empty shell of film, where all the elements that move me are replaced:
Character development for cheap plot devices
Muscles and physique for character and personality
Snappy dialogue instead of introspection
Regurgitated themes instead of original thought
Not all superhero films fall into to this in my mind; I did like so many elements of Batman Begins, and most of Joker (sans my usual complaint about Robert De Niro making every role just feel like an interview with him as a person and no actual character creation). For me I just like good film, where it feels honest and smart, and it moves me in some way.
When I think of sequels in general, I just see the desire to turn original art into reliable revenue streams. Smart business idea, but antithetical to art. I'm very cynical about Hollywood in general, that it's just business and destroys much of what it touches, but I do think there can always be meaningful film, and that's what I hope for.
Like, the reason the Joker film hit me was that it really did explore psychological themes with intelligence and respect for the audience. It gave air and space to important elements that transported you to a place to gain empathy, nuance, and horror. To me it was a real film.