Saitama isn't a gag character. He isn't infinitely powerful. He has the potential to be as powerful as anyone he fights as long as he isn't obliterated before he can grow.
So, right now, we're going by feats and logic, not by saying "oh if the creator says he's better, he's better", yeah sure, you can make an ant strong enough to destroy planets in a fictional story.
Take his fight with Genos for example. It literally showed a chart of him growing more powerful (exponentially more powerful, but he was growing) as he was fighting. However, none of his feats have gone beyond planetary. I'm sure he could destroy the solar system at this point, but not with one shot. If he fights someone who CAN wipe out the solar system in a single shot, he'd probably end up winning. But if he fights someone who wipes out the galaxy in a shot, he's done for.
People put him above characters like Goku, but my guy. He doesn't have any feats above planetary. Goku has shown universal feats. If you want to use the term "outerversal", he has shown those feats too, but so has everyone else at the tournament of power...technically. Moving in a space without time would require infinite speed or the ability to add or control time. Also "shaking an infinite void" would require infinite power.
Note: Dragon Ball's writers are retarded with any logic and consistency beyond kindergarten, but regardless we're gonna not talk about those two feats right now.
Considering how strong Goku was when he was fighting Beerus, he's well into the multiversal stage right now.
How tf are y'all comparing a dude that has so far barely shown planetary feats to a dude that can slap universes out of existence? It's like comparing a flea to the sun. There are plentyyyy of fictional characters that would think of Saitama as barely a fly.
Don't get me wrong, OPM is insane and the powerscaling is good and consistent, but you can't compare Saitama to gag characters or characters like Goku. kthxbye