He doesn't have absurd advantage state like the top tiers, who are consistent tournament threats not only because they are good but because they can win games consistently and quickly. So, its hard to adapt to a top tier player if they kill you with a kill confirm before you really get a read on how they're gonna do it; this is more true the more kill options they have! He also doesn't have the crazy disadvantage of the games queens, and is actually pretty gimpable. Of course, good play can largely negate that but its something other characters don't have to worry about and is a problem vs MK, pika, and sometimes shiek and CF (probably some others im forgetting). So he doesn't have the get out of mistake free card that is a livesaver for many as they move through bracket.
No, what mega has is better than that. Before those adv/disadv states come into play, we have the neutral. Mega offers complete neutral dominance. Some MUs, like DDD and ganon, are really easy because of how hard this dominance is. Others, like luigi, can wreck us when they get in and still lose the MU because the wall of mega is that good. This is a top tier threat, we even break even vs ZSS because our neutral is better. Some say the MU is a problem, but I have heard MK also doesn't like playing us. As we get better and better at keeping people out ( I think we can utilize more rising airdodge and spring escapes personally, our landing is waaaay above average due to leaf shield) this will only get better.
Additionally, this metagame currently places huge emphasis on kill confirms. Unlike most unlucky mid tiers, we do have these kill confirms! Downwards saw blade into u-tilt kills crazy early, and when that stops working usmash keeps it real from the same setups. Additionally, DICIT forwards confirms into utilt and usmash (and if youre fast, bair)! Top tiers also have super early kills from 50/50s, 33/33/33, whatever... We have really really deadly tornado traps, which I think we need to explore more.
Falling away with someone with your back towards them is a really scary position for them. Megaman's bair is frame 4 and kills with huge range, its one of the best bairs and its a big reason I believe in and play megaman. This naturally causes airdodges, but these get eaten if you wait and bair OR start hitting tornadoes. From here a couple reads works with momentum physics in this game and can roofio them from absurd percents. The tornado itself does super high damage for an aerial (hell, for a smash) as well, so even if they escape you basically accomplish what a long BnB from a top tier does in damage. I've also baited an airdodge from diagonal below by jumping, jumped through them and gave them the business end of a dair.
I see megaman like brawl olimar. I think it was dabuz said about his MU with MK (paraphrasing obv): 'You basically have to win neutral a lot more, but you have the tools to do so'. Thats where we are going. I already have people saying 'wtf do I do vs megaman'. Lets make more people ask that!