SLS doesn't serve any actual NASA needs. It's fake make-work. Case in point: Congress expressly ordered NASA to launch Europa Clipper on SLS, to make it appear that SLS was indispensable to core NASA science missions. But, due to design flaws, SLS turned out to be technically incapable of launching Clipper at all. So they backtracked and allowed free-market competition to compete for the Clipper launch. Which it did: a very, very cheap Falcon Heavy launched it instead.

Which it was capable of doing all along—Congress and NASA lied about this, misled the public, to make it appear that their jobs-creating, pork-barrel project was serving some genuine need NASA had. It wasn't! They had alternatives all along—they were pretending they didn't.

When you read about these things, you have to know all the actors you're getting information from, and what motives they have to mislead you.

There's not a single real mission in NASA's budget, or conceivable future budget, that needs an SLS—full stop. Sole exception being the moon project, which was created with the express purpose of finding a problem SLS would be the only answer for (and even that's now in doubt, what with Starship).