Its very much the kind of niche thing that the format allows for and to some extent encourages
With Fusion Summons growing ever more important in the current metagame thanks to decks like Branded Despia, Super Polymerizations potential in the current meta only grows larger as time passes
First of all, its cheap and an instant
Piglet is a Super Rare and the first time this character is making it's appearance in Disney Lorcana
On top of all that, he can passively build up lore for each action you play, giving Lorcana a spellslinger-style deck that could be a big threat if not answered quickly
Once per turn, during either player's Battle Phase, you can target all Spellcaster-Type monsters you control, those targets gain 200 ATK for each card in your opponent's hand