I have played Pichu for a bit now. Bear in mind I am not terribly skilled. I am good enough to beat tournament-competitive players on occasion, and most the people I play with nowadays are a similar level below me. They are the sort that will practice highly technical movements on their own, but I am the sort that focuses one ideal positioning and solid basic gameplay.
For me the issue with Pichu right now is that he feels insufficient as a Minus character. His moves are not flashy or particularly powerful in any specific way. He seems highly technical without anything else backing him up. Take fox as an example, he has a range of additional gimmicks that make him interesting for all players. Pichu right now just has a notable disadvantage and nothing paired with it.
He has less mobility than Pikachu, but is lighter.
He has a mine, but it is the worst mine in the game - way below Toon link or charizard.
His down B is buggy, but even if it wasn't it wouldn't be very interesting. He lacks sufficient mobility to safely use it off-stage.
Most distressingly, he doesn't have any particularly interesting gameplay abilities at all.
He doesn't charge electricity to release in attacks, he takes self damage but isn't deadly. He cannot engage enemies particularly well. He has no real projectile play. He is not mobile.
Personally, I don't care much about appearance, but this Pichu just isn't interesting, and doesn't fit in very well with Minus in my opinion.