Lee has more walks (5) than strikeouts (4). He's hitting the ball. He has a .143 average but his statcast page is bright red including barrel% and hard hit%. The hits will fall if he keeps this approach.
He's fielding fine at 3B. He's still slow but sending him to AAA isn't going to fix that.
If you're going to give a rookie a chance, he deserves more than 8 games to establish himself. This is especially true if he's been holding his own over those 8 games. Lucky for Lee, we won't see Lewis for a couple more weeks.