>>49955589A lot of popular Gen I Pokémon suffer from this not out of malice but probably just because it's hard to correct these things short of rebalancing or handicaps (like Charizard's Megas). Pikachu itself is absolutely awful to use in Yellow—worse than Wigglytuff because at least the latter has a little bulk and can use STAB Body Slam. Given its inflated HP stat, I suspect they intended Wigglytuff to be a kind of midground between Clefable and Chansey, but that just made it worse than both. Unlike Pikachu, it also benefitted from the splitting of the Special stat in Gen II, which I suspect was an intentional attempt to make it more usable, but it obviously wasn't enough.
In hindsight, Wigglytuff probably should've been made more physically oriented to fill a different niche to Clefable. Clefable has just been lucky since its original stats were solid, its movepool was nuts, it was given good abilities, and there was no way the "Fairy Pokémon" wasn't going to get Fairy typing, so I think it's just a beneficiary of cumulative decisions that gave it more advantages rather than a deliberate handicap. Wigglytuff has been given a few similar boosts but because they've all been pointed in the same direction as Clefable (Fairy typing, Sp. Atk increases), it just ends up playing second fiddle to it instead of having its own identity.
