Final smashes are lacking for the following reasons:
-All of them are unbalanced af. Some are worthless, some are godly.
-No special graphic effect / cool sound effect / what have you when you pull off one. Just a measly zoom on your character.
-Generic and unfitting for the most part... Giga Bowser?
-Cloned finals, hello that sheik light arrows
-The zoom on your character. Rosalina's final smash is so horrible, that it is more likely to screw with somebody recovering off stage with its zoom, than getting an actual KO. Poke trainer's FS zoomed in for like 6 seconds too.
-they're janky. For example Ganondorfs turns into Ganon, zips off stage in a static pose, and then he just pops back offstage without graphical effects. Several FS are like this and need fixing.
-glitchy (at least in Brawl)
-they're mostly lame. Rob goes crazy and shoots lasers from his eyes, wow so cool. Jigglypuff puffs up. DK should jump into space and punch the moon so hard it falls onto the stage, not play bongos.