Your opinion doesn't really matter, that's hard statistics and science on this. For most measurements of athletic peak, it's between 22-28, but that 28 is beginning to slide back closer to 30 with advancements in science, nutrition, medical procedures and PEDs. These stats also largely correlate with most major sports that are ran semi meritocratically. Be it the Olympic sports or major sports Tennis, NHL, NFL, NBA, MLB, Rugby, Soccer etc. And to an extent Boxing and MMA, but they're more business driven so you see guys at the top stay longer age wise often and some guys that rise take forever to get to the top despite being obviously amazing due to business.
MMA takes forever to be really good, only now are we seeing the age fighters can go pro get more commonly turned back from 18 to 15-17yo in places. Only recently is it truly a global sport and one where guys are regularly competing amateurly at 14-17yo. But a kid like Kyouma got badly exposed in his last loss in a way that will take years to properly address for when, if he ever, makes it to an elite level. Who knows what else needs drastic work and exposure and growth and discovery for him too..probably a lot.