@mister_nobody I know, right? I really don't get how so many people call most chapters "filler" and seem to only want Saitama to show up and kill everything in one punch. (I'm not saying that the commenters for those two things are the same ones, but they are still both present.)
They don't seem to understand that beyond the title and the first few arcs, the series isn't really about Saitama. He's actually one of the least interesting character in the story. As for his story(Saitama's), it's not being developed in Garou's arc precisely because most think of him as irrelevant (in-story) and he is thus not called to action. Furthermore, Saitama's story and personal character growth is one with such a high hurdle (needing to face beings capable of fighting back against him) that it's more so an over-arching story in the narrative of the One Punch Man series.
It doesn't make sense to only focus on him since nothing really happens to him other than accidentally getting mixed up in the story threads of other characters at opportune moments.
This way of doing things is precisely the reason why One Punch Man works as a series going beyond it being a simple repetitive parody. If One Punch Man was always focused on Saitama, it would just end up being a series consisting only of chapters like the first few ones (essentially "monster of the week" chapters, and with even monster like Boros being no more than that since context and characterization (of all characters and societies involved) are what elevated Boros' arc into more than a "monster of the week" one).