I actually think it's simple.
He's at his best when he's basically a 'goal-hanger'
Ancelotti knew the score. Told him to stay near the goal. Calvert-Lewin is a very decent poacher. He's not good at bringing others in to play, and he's not going to score outside the box. I think most would agree with that...
The issue we have at the moment is then is....
1. We're so bad, we're not creating anything at all. He used to have a threat coming in from Digne, or even Sigurdsson/Rodriguez. Digne/Sigurdsson/Walcott/Richarlison topped chances created in 2019/20 when he scored 13 league goals. In 2020/21, It was Digne, Rodriguez, Richarlison and Sigurdsson when he scored 16 league goals.
Who is creating chances now in this Everton team? Iwobi is 2nd (joint with Gray) for chances created in the league this season, after Richarlison.
2. His fitness isn't there, and I suspect his form/confidence is really low. Often the two are hand in hand.
With no alternatives - we need to play him into form and fitness. We need to find someway of actually creating something for him. He gets sod all from the full backs. Put him in Aston Villa's team with two full backs who can actually cross a ball, and a playmaker in Coutinho and and you'd see him scoring.
Everton are experts at setting players up to fail.
Calvert-Lewin has made, what? 9 appearances this season. Come on...