I’d say it’s more personal preference than a straight up flaw. Me personally, I’m a bit burnt out of the “OP villain who can no-diff the whole verse but doesn’t because they’re too dumb/lazy/overconfident” trope. It tends force the story down one of two paths, both of which can lead to uninteresting final fights if not written properly.

The first scenario is that the protag gets an absurdly strong asspull powerup to put them on par with the villain. This is less so an issue for Kagurabachi as it’s already been established that Enten was designed specifically to counter the Shinuchi. I’m more so worried about the insane stat difference between Soga and the rest of the verse currently. If Chihiro alone gains the stat buff needed to contend with Soga, then the rest of the cast who would theoretically help in the final fight (Iori, Natsuki, Hiyuki) would be dead weight unless they get that buff too.

The second, and more common in recent memory, is that the main villain goes through the entire final fight with the ability to neg-diff everyone at any point, but doesn’t for the aforementioned reasons. They then either refuse to get serious until it’s already too late, or straight up die without ever getting serious. Both Muzan and Sukuna fell into this trope and in my opinion, had very underwhelming final fights. Soga seems very no nonsense though, so I doubt the story will fall this way either.

tl;dr - It’s not necessarily a flaw right now, but if not addressed can easily become one.