Devoe is getting 21 min/game, which is right about average for the team. However, he has taken the 2nd most shots of anyone on the team with 114 (behind only Westbrook with 131. He led the team in shots taken again today with 12).
More shots and more time aren't Devoe's problem; it's the % of shots he's making (3rd worst on the team for three point %, ahead of only Cobbs & Williams @ 33%), as well as his decisions when he's in the game (tied for most turnovers on the team, shot selection, etc.)
If he can improve on those things, he'll most likely get more time.