I feel Nick Gibbon is not convincing

I watched Ferroequinology (2021) and Nick Gibbon was one of the parts I kept noticing. The role needs more detail, but the performance stays on the surface. Some emotions are too simple, and I cannot believe the character enough. I do not hate it, but it did not pull me into the story. For me, it does not feel very real in many scenes. Many moments pass very fast, and I do not remember much after them. This is only my personal view, but the performance changed how I enjoyed the film.