I think the difference between Star Wars and Alien is all in the tone.
Alien is established, from the outset, as a dark film. It’s horror! The characters make bad choices and we fear with them. Darker films like this often critique social issues as it fits the tone. So Alien’s critique on capitalism works.
Star Wars, on the other hand, is not a dark film. It’s fun escapism. This is why so many call Canto Bight “not my Star Wars” because they want an timeless story separate from the real world.
That is not to demean either approach. Critiques on our society are often well called for while timeless tales are a lot of fun to watch.
The interesting thing about the Last Jedi is it tries to renounce it’s escapist nature. I don’t really think doing this on the 8th episode of a 9 part saga is a good idea, but Rian certainly tried to make TLJ into a “dark film”- Canto Bight and Luke are some examples. You know, I’d be willing to see how a Dark TLJ turned out.
Unfortunately Rian opened the film with a yo mamma joke, instantly eliminating any chance of a darker tone. What we have now is a confused tonal mess.
It’s funny that you say Canto Bight takes away from the “timelessness” of it all, because that’s a part that to me feels very much timeless - it feels equal parts Hitchcock and Dickens, amongst many other disparate ageless things. I don’t think political there’s anything going on in that sequence that’s explicitly modern (though I guess many do?). As to “separate from the real world” in general, I’d argue SW has never been that.
Anyway, a darker tone is not a new SW thing that TLJ introduced. Johnson included humor throughout to keep it fun and escapist (i.e. to make sure it didn’t renounce its escapism). Opinions on execution aside, a film can be dark and fun/funny at the same time - ESB is a good example but, on the former topic, I think Aliens has some good humor too.
Otherwise though this is a better point than the others I’ve read. Rather than basically just saying no comparison exists when I can clearly see one, you’re saying maybe it’s more a matter of it fits SW less. I disagree of course, but it’s more reasonable (and reminds me of the arguments against the PT’s over inclusion of politics impeding the escapism which I think is a bit more valid but for different reasons).