I see a lot of Megaman players on the ladder. And, looking around the Sumabato bracket between matches, I was surprised by the amount of Megaman players there. It makes sense in their meta, more defense and reactive, since he basically sets up a bullet hell style situation with hitboxes flying all over the stage while he dances around with really, really solid mobility considering his weight.
Mario is a problem. It isn't the same problem most have with Mario either. Well, it is, but megaman doesn't really have a good escape option (rush isn't intangible until too late to be amazing like spring) and is heavy, so he gets combo'd HARD, even harder than most. And his disadvantage isn't great offstage, his recovery is punishable, so a Mario BnB that puts him off the ledge and plays on that has a real chance of doing 80% plus. The speed at which mario attacks and presses buttons is annoying, for instance I'll do a downthrow metal blade while falling back to stop him, he'll come in with his RAR bair and grab the blade, hit my shield, and be safe with my metal blade stolen! Or, he'll dair and itll beat out small hitboxes and still hit me. Mario has a reflector, which hurts non-pellet long range zoning significantly. It also ruins fsmash traps, such as landing a crash bomber and using it to cover f-smash's recovery, or just a simple f-smash charge at the ledge. He puts buttons out so fast its unlikely you'll land a stray utilt to help get the kills, so you're off hoping for a bthrow which is meh unless you're near the ledge, since Mario is a fat *******, or hitting a bair which is possible but less and less likely as Mario's learn to just respect it.
Speaking of which, bair is a serious contender for best bair in the game. Kills, does respectable damage, is disjointed, and has good range, all starting at frame 4! Downsides include it being multi hit so if you trade you usually can't get the killing blow, it having bad landing lag, and it almost never connecting out of a SH against a grounded opponent unless you are wayyyy to far into them to even pretend to be safe.
Captain falcon is also a problem. His stupid jab beats pellets straight up, has deceptive (stupid) range, and covers behind him. His smashes eat projectiles and still hit, killing megaman early. He can edgeguard megaman about as well as we edgeguard him, but you have to hit falcon a lot to get him to finally die offstage (unless you hit a dair, which isn't a good risk/reward against falcon. Its slow enough that he can reasonably expect to dodge it frequently, whereas bair should rarely miss, so its highly suggested to go for bair). Nair sends him at a bad angle and is usually a great edgeguard due to pellet protection, but falcon will just grab you from 50 metres away. His dashgrab is his dashgrab, its a good zone breaker which obviously is problematic for a zoner. His power is just really strong in the MU.
Speaking of which, Megaman is hard to make succeed in a bracket situation. Your games are long, which can be tiring. They are more likely to end quickly if something goes wrong than they are to quickly swing in your favor. Rage monsters like ZSS and Rosalina can quickly eliminate a megaman since he racks up a bunch of damage from silly rage setups. Random MU's like Palutena are tougher than you would think, and the ones that are logically tough like Falcon and Mario are really common. Like, really common. Mario is everywhere, even for just a 60-40 its tough to fight so many. And his gameplan is essentially the same vs Megaman, so knowledge isn't a weakness. He can learn specific stuff and improve like any MU, but he isn't clueless going in.
That said, Megaman is a cool character! He can work in many different ways (seriously, check out sonicmega vs Scatt's playstyles). I've been working on a more aggressive megaman, since I think there is power in being able to use his kill setups in a more hectic environment. Down angled metal blade into utilt is a kill confirm, and the utilt sweetspot kills insanely early. Also, it has huge hitlag and feels awesome like a Dragon Punch should. Bair is one of the best offstage and rising kill options, even when staled. His grabs are huge, can be augmented with leaf shield to add 8% plus his 3% pummels plus a 12% are Ryu level painful.
But the Scatt playstyle... I understand that people hate it. When I play with my housemates' casually, I almost never bust out megaman, and when I do, I don't use any pellets. The reason he won't get any buffs are his good MUs. If you struggle vs Megaman, its because you struggle getting through pellets. You'll be trying to make something work while the blip blip blip slowly tears you down, then you die to leaf shield -> roll ->bthrow at the ledge before you realize that he kills that way, or eat a RAR bair when you thought he was going to just pellet your landing ("he's been pelleting for 10 minutes, why would he stop?"), or just get utilted when trying to roll thru pellets... It just makes sense, if you can deal with the pellet salvo efficiently Megaman has trouble zoning you with mediocre tools (excluding bair, utilt) then its an uphill battle, while if he can keep you out its his game to lose. Especially in America's aggressive meta, I understand why he isn't a popular choice.