They often do criticize these movies based on what the movie is trying to say. They’re not comparing them to movies in other genres.
Superhero movies are often formulaic, predictable, overly rely on CGI, have shallow stories and plots. Logan, The Dark Knight, Spider Verse etc. were praised by critics for not committing the same mistakes other super hero movies do. The criticisms describe what kept the movie back from being a truly great super hero movie, not what kept it back from being Citizen Kane.
And even after all that, they’re still subjective opinions. You don’t have to agree with them on what a better super hero movie looks like.