Foundry VTT is great, but like any software, it has a learning curve, especially for people coming from Roll 20 who are used to things being different.
Having a world created and available that can serve as a tutorial would be great.
First scene with a hello, some arrows pointing at the UI elements, and explaining them. Maybe a module (actually we can add scripts to a world itself, just as if it was a module) which pops a dialog that guides the users through various things and can listen to hooks to know if they executed the action suggested.
Roll20’s tutorial game is absolutely horrible and non working, but it serves its purpose, and not having something similar for FVTT can hurt a lot of new user’s experience.
Having maybe one tutorial for GM tools and one for player tools could also be beneficial. Or the same one that just checks if the user is logged in as GM or not.