I absolutely love Realist Hero, and at the moment it is my straight-up favorite light novel (though Bookworm is a close second and the main reason I put Realist Hero ahead of it is simply that more stuff has happened in Realist Hero, as far as official English translations go, so they might switch places later).
When it comes down to it, though, Realist Hero is ultimately another feel-good "MC solves all the problems" power fantasy LN, hence why things ultimately come fairly easily for him. The fact that there's an in-universe justification for why things are easy for him just highlights the nature of this series. It's ultimately different in nature from Bookworm, so I wouldn't really make any direct comparisons between the two. If anything, as far as its tone and nature goes, it's closer to Smartphone (albeit with less of the silly stuff, but hey, both have polygamy and country-building so...).
However, the way Realist Hero executes its power fantasy, at least for me, just works so well. Of course, it helps that Souma has no real OP powers and largely has to rely on his smarts and making good use of the more OP people around him. But I think what makes Realist Hero so good is how the story ultimately revolves not around "saving the kingdom/world" (despite the title), but rather about the characters' feelings and how they all have their own stories within the larger story. The frequent changes of POV helps a lot in this way, and I really like how many side characters have their own relationships outside of Souma's harem.
It's very telling that the very first scene of the story is Souma's grandfather telling Souma to find a family to care for. The first scene of a story should set the tone for the rest of the story, so why have a scene like this rather than, say, Souma talking about Machiavelli with friends or something actually related to "rebuilding a kingdom"? I think it really shows how the focus is really on "family", with the "rebuilding a kingdom" part being the framework that feeds into this theme. And that's what makes Realist Hero such a great series for me; it is a power fantasy that goes beyond just "doing stuff" and feels more like a personal story.
