JACK-OF-ALL-TRADES
A person who tries to do everything, but ends up doing nothing well. They’re like a kid with too many toys, can’t focus on any one.
He can cook, clean, and paint, but he can't focus on any one of them for long.
She can write, sing, and act, but she can't be called good at any of them.
He can fix a car, build a deck, and cook, but he can't do any of them well enough to be proud.