>>280334558
>>280334940
I'd say that's more the result of OPM pointing at the powerlevel barriers you often find in shonen and such and taking that to its logical conclusions where 'only the S-class matters' is the unspoken rule, even in universe.
Most A-class we've seen aren't weak or anything, compared to the lower classes, but as that one page states: S-class is just insane.
Promoting into incompetency does still seem to be a problem in the MA, though, with Death Gatling's hit squad being largely composed of B-listers, that I recall. Preemptively: It was from the manga, yes, but that was before that went off the deep end, and clearly had something to say, unlike most of the later bollocks.
