I look at Marth and see a comparison to Mewtwo as inevitable. The two can kind of do the same thing, but just take a look at Mewtwo's advantages over Marth:
- Way, way, way better options out of dash. What does Marth do? Dolphin Slash? Mewtwo's insane dash attack and strong up-smash are leagues better than that.
Dancing Blade, Jumping and doing an aerial is an option. You could just not run a lot to begin with. Foxtrotting and Dash Dancing are options as well as walking.
- Better anti-zoning game, with the best projectile in the game (or among the best), on top of a reflector
Not much to say against that. Different characters, different tools. Don't really think Marth needs a projectile even if he had the option for one.
- An easier time killing. Marth, to his credit, can kill very early with the appropriate tipper read, but a kill throw at a reasonable % is way more consistent, and f-air not having to be tippered to be destructive is great. Plus Shadow Ball.
- Better grab reward. Marth has a better pummel but Mewtwo's f-throw is bonkers. Also worth repeating because kill throws are that important: kill throws!
I usually mix up with grab releases and throws. You can get tilts afterwards and if they shield too much you can go for Shield Breaker. Throws could use some more damage, as of right now they only do 4-5% I don't feel like 6-7% throws with adjusted knockback to make them the same (except uthrow make that thing stronger) would be anything crazy.
- Better overall mobility. Marth has better air accel and traction, but Mewtwo has better run speed, initial dash, and walk accel, on top of his super incredible airdodge, which lets him move in ways Marth couldn't dream of, both in neutral and disadvantage.
Again, different characters, different tools. Don't really think Marth needs Mewtwo's run speed considering his gameplan.
On Marth's side, he's heavier, and his arcing hitboxes (very important for a swordsman character) are better on the likes of f-tilt and f-air, but it's hard to argue that Marth wouldn't love Mewtwo's f-air and d-tilt in exchange.
Personally, I prefer Marth's fair hit box.
Thinking of it that way, Marth buffs don't sound so ludicrous to me. Right now, his "sell" is early kills via tipper while sporting a solid neutral game, but Mewtwo kills more consistently, is more flexible and arguably better in neutral, and gets more rewarding conversions.
Mewtwo also dies quite a bit earlier than Marth. You can slightly screw up in neutral and be okay with Marth. If you make mistakes in neutral with Mewtwo, you're gonna have a bad time.
This does not make Marth unplayable, of course. In fact, I think that he's a decent character. But just as Lucina sort of lives in Marth's perpetual shadow, I think Marth also lives in Mewtwo's shadow in the current patch cycle.
They're two characters with different play styles. I don't see how one could over shadow the other. As of right now, and possibly for the rest of the game, Mewtwo is better, but it's not because he's just Marth but better, he's just a better character.