ok this thread is hilarious
but here ya go:
mewtwo's weight + double jump creates an uncomfortable position where mewtwo gets
a combination of resilience to throw combos (most throws can't set up on mewtwo because of how heavy he is),
a better crouch cancel (a buff that is accentuated by a ton of new powerful options out of a crouch cancel like confusion, disable, uptilt),
the option to simply trade hits over and over without really thinking about it and convert a decent trade into a good combo without really worrying about how much damage you took in response,
an unexploitable recovery that can get the ledge, the stage, or well above it in the blink of an eye (a trait not shared by similar high survivability characters with good recoveries like peach, samus, ROB, Snake who can all get hit out of their recoveries and either die or take a ton of additional damage)
with these traits in mind frankly it doesnt matter if mewtwo's a big target, he has the best survivability in the game right now. mewtwo can just CC, tank a hit, get a nice dtilt or confusion or w.e, smash the opponent with whatever combo (yes you can combo floaties who the hell said mewtwo has an inherently harder tiime lol), edgeguard them faster and more fierce than anything puff can do owing to a super fast SUNC that resets his double jump or teleport that puts him right back on the stage.
nerfing his weight gets rid of a lot of these undesireable traits that make fighting against mewtwo a drag and focusing him more of a somewhat frail offensive powerhouse with "difficult" approaches rather than someone who can outlive ganondorf and has the recovery of better than puff with the combo game of falcon with "difficult" approaches.
in contrast nerfing his double jump is kind of a lame idea that nukes a lot of the fun momentum based options he gets on double jump and he'd still have a pretty good recovery and would still be able to bully people on stage easily and still be able to gimp effectively with SUNC resets onto the ledge. also the double jump **** ttakes a dubious amount whereas weight is like lol i held down lol i do 70% damage combo cuz im fat