I don't know why you folks are such a big fan of Ryoufui. He is great, but not that great to say the manga went downhill after him.
For me, Kingdom was at its peak when Riboku-Houken duo terrorized the entire China. Damn, the way Houken destroyed Gekishin was incredible.
Bruh..Ryofui >>>> Houken
Honestly Houken always seemed like he doesn't belong in this manga. He always seems too strong for Kingdom verse, it feels he actually belongs somewhere like in Naruto world.
Same applies to Kyokai, but Houken was more extreme example.
While Ryofui was really great.
How can he blatantly told the King "I was the mastermind behind your murder attempt last night", and the King realized the truth but couldn't do shit but "ahaha you must be joking Chancellor".
That's just his debut. Dude made the biggest debut not only in Kingdom but in manga history.