The whole Bayo compared to MK discussion was started by a mention of a tweet from Ally where he said, jokingly or not (I have no idea as I haven't seen the tweet) that Bayo makes Sm4sh not fun for him. Fun is entirely subjective and I even mentioned that unless Brawl MK was ledge stalling my Wolf, I much preferred going against MK than I do Bayo.
Bayo has bullet artes to force approaches, an amazing recovery that isn't quite as reliant on double jumps, can't be ledgehogged and has a wall cling/wall jump and doesn't enter helpless, has long lasting aerials to make edgeguarding or trapping landings easy, has a f1 air dodge that's amazing in most situations, requires murdering of the left thumb to even attempt avoiding death or massive damage from her combos which can start from a large pool of moves including a f4 OoS option and has a f5 counter that works just as effectively on the weakest jab to the strongest smash attack or special that can lead to the previous mentioned death or massive damage.
Brawl MK is by far the better character with his long, unclankable reach, fast startup and endlag, still amazing recovery, insane edgeguarding and power and ability to stall on the ledge. But all of that, for me personally was more fun to go up against than what Bayo has. More fun to fight against =/= less powerful.
You also can't just look at the tools Bayo and Brawl MK had but the tools every other character in the game provided. I felt more capable of handling MK with Brawl Pika and Wolf and the options they had (like QAC anywhere on stage, stronger edgeguarding, DACUS and Wolf Flash cancelling) compared to Bayo and the options Mewtwo, Roy and Robin provide me.