I think that's actually why Houken feels less annoying to me. Houken from the outset is presented as the exception to all the rules. He's not a general, he's not a soldier, really he isn't even a warrior. The dude is presented as, and feels like, he comes from a different world than the rest of the players in the manga. The fact that he isn't part of the standard rules is what makes him ironically feel more fair, yes he's a copout but he's a copout by design, a copout is all he'll ever be.
He doesn't have a retinue, he doesn't command an army, he isn't driven by any loyalties or any base desires, nobody really respects him or looks up to him, he's not a national hero of any stripe, he has no history that isn't personal, he doesn't have a trusted friend or a close rival (unless you count Shin but Houken never sees Shin as a rival and never treats him like one). Houken is literally nothing but a walking exception to all the patterns, and that's what makes him kind of acceptable. We are also shown in the very arc he becomes relevant that he has real weaknesses and is fundamentally flawed; it's the kind of flaw that 1. makes sense in retrospect 2. gives a real hope for his eventual defeat and 3. is an actual flaw that isn't "heh, he was too strong for his own good".
Meanwhile Shibashou by all appearances is just Moubu, but more powerful, more bullshit, with even more tier 3 cavalry in his army, with less foreshadowing, less backstory, and coming at the tail end of something like fifty new characters none of whom survived more than one arc. Shibashou is not presented as an exception, but he still doesn't obey the rules, and he feels like just the latest bullshit hand trap that Riboku has that's robbing us of a good confrontation between some of pre-Imperial China's biggest strategic masterminds. The only difference between Shibashou and the tunnel is that Shibashou breathes.