This is looking at the problem backwards and is just not really true. His shot volume is absolutely fine. He needs to get better at when he shoots, sometimes he takes too long, sometimes he doesn't shoot at all when he should. Sometimes he shoots when he needs to pass, but his role in the team is to provide end product and he needs shot volume for that.
Garnacho has 6.2 xG from 72 shots, the Caf darling for his place at the moment is Cunha who has 7.3 xG from 88. Garnacho's average chance is 0.086 xG, Cunha's is 0.083. Eze has 7.8 xG from 89 shots at an average of 0.087. Those players are 25 and 26 respectively. The main difference between Cunha and Garnacho is Cunha's having a freakish season in front of goal (which he'll never maintain, and is why we should stay well clear), Garnacho is not. But then guess who underperformed his xG season after season until he hit his mid 20's as well? Yeah... Cunha... These things take time.
He's well within the normal range for a team that relies on him as the main outlet on the break and can't dominate possession, arguably ahead given his age. He'll never work out how to get better unless he's allowed space to make those mistakes and learn from them.