No character is bad in 64 if you'r Isai. Almost took Apex 2012 with Link. Lost to captain falcon.
Smash 64 isn't really clunky or slow; learn to L-cancel all your moves and then just get your opponent above like 40%. The hitstun in smash 64 is ridiculous, meaning you can get insane combos you can't even dream of in ANY of the other smash games. It really allows for some amazing creativity if you just watch your opponent's trajectory and learn to follow up correctly. Just look up "Isai Alvarado" on youtube and watch his videos.
Also, as many bombs as you can pull before the first explodes is how many bombs you can have in play, so there's that.