JACK-OF-ALL-TRADES
A person who knows a little bit about a lot of things, but can't be called an expert at any of them. They’re like a pizza, tastes good, but no one thing stands out.
He can write, draw, and sing, but he’s not good enough to be famous at any of them.
She can cook, clean, and sew, but none of it is amazing.
He can fix a car, paint a house, and play guitar, but he can't do any of them well enough to be proud.