After one of the latest macOS updates I can't work with Apple's default SF fonts in AE 2020 and AE 2021. All scenes with these fonts are very slow, After Effects starts to slow down, even if the scene is very simple and the text is not animated. A colleague faced a similar problem after the latest macOS updates. Because of this problem, it becomes impossible to work on animating iOS app mockups, all working files with these fonts became unusable.
I suppose, that problem happens because Apple updated all their SF fonts, but AE was not ready to support variable fonts.
Error or problem
User interface or workspaces