Noobs don't like Jiggly because Jiggly isn't a cool :
Pretty boy with a sword/bow (Link, TLink, Ike, Marth, Pit)
Manly man (CapFalcon, Ganondorf, Snake)
Kid(s) with special powers (Lucas, Ness, IceClimbers, Olimar, Pit, TLink, PokeTrainer)
Human girl (ZAMUS, Zelda, Peach)
Franchise Main (Mario, Samus, Link, Kirby, Pikachu, Fox, Sonic, Snake)
Animal Humanoïd (DK, Diddy, Space furries)
"Evil" (Bowser, Ganondorf, Wario, Wolf, MetaKn)
Weirdo (G&W, Luigi, ROB, Wario, Olimar, Dedede)
Mysterious (Shiek, MetaKn, Snake, Lucario)
-Remaining : Yoshi & Jigglypuff (Cute & Lovely ISN'T Cool)
The Melee -> Brawl change hasn't be beneficial for the Competitive Jiggly. Melee Jiggs rely on combos and with reduced hitstun there is no combos. Jiggly's best move is nerfed (Low knockback & Outstage Rest is "now" dangerous because it will be a Star KO). Some Melee characters rely on "combo to powerful move" but without combo (and/or powerful moves) it's hard for them. *cough*Captain Falcon*cough*
Good points :
Run faster (WTF, Jiggly can run ?)
Jump higher (It's harder to combo a good WoP & you can always comeback anyway...)
Still awesome Recovery (but everyone has it too...)
Jiggs still ***** low levels but she isn't good against pros using defensives moves...