There's more to the issue than that, though. Any genre can be explored at any length of literature. It's just that you can tell different tales in a haiku or a short story than you can in a novelette or a novel or a series. A skilled author suits the length of the story to the amount of complexity it contains.
That's where it gets complicated, because historically, certain sizes have been favored whether they were good for a given story or not. There was the "dead zone" between short stories (capping at around 7500 words) and novels (starting at around 40,000 words). There's been a recent trend towards frankly bloated novels where big publishers didn't want to see anything under about 80,000 words. You know what it looks like? A 50,000 word novel with 30,000 words of padding.
One cool thing about weblit and ebooks is that they're killing those problems. While the favoritism is still active, there are now venues for other stuff that falls outside the narrow target range. So if you love reading fiction between 7500 and 40,000 words, you can now find lots of it. If you write it, you can sell it. Yay! Yay! Same with shorter novels. Then there's the serial. Those used to be super popular in magazines and newspapers. Then they nearly died out. Now they are back. Online audiences love serials. So if you like to tell or read rather long stories in short pieces, you can do that again. Yay! Yay!
I'm exploring much the same ground with poetry. I can write and sell short poems, or long poems, or epics. Okay, my epics are a lot shorter than Homer's but by the time I finish a series, I do have about a book's worth of tale in it. I think that's cool. Serial poetry hasn't seen much attention even in historic times. There are some examples but not a lot. So it's up to me and my audience what we want to do with this. Yes, I can do worldbuilding very concisely. I can also spread it out. I can even easteregg it and rely on my very savvy readers to snatch things out from between the lines, crack them open, and dance around with the chocolate candy yelling, "Hey, look what I found!" I think it's awesome when people reveal hidden meanings, connections, and implications like that. The size, then, is a matter of personal taste for the poet and for the audience, balanced against the demands of a given poem -- with an option to elaborate across multiple poems if so desired.
Science fiction. Weblit and ebooks. Paper too, if you like it, because there are more option there now in terms of alternative publication. Pick whatever length you want to read or write. Go have fun.