GameMaker is generally excellent and decades worth of material, it's original design was to teach students (disclaimer, used to work for YoYoGames a long time ago) not sure where it sits these days, but suspect it's only gotten easier to work with.

I just started tinkering with Godot, seems very, very good and the licensing means you won't suddenly have the rug pulled out from under you.

I'm torn though, the recommendation for things like Roblox seem valid, but indeed it seems like the kind of thing where you will hit a glass ceiling. On the flip side getting started on something more generic may be tedious and cause an 11 year old to lose interest quickly.

I think it comes down to the motivations and nature of the individual - do they wanna learn the skill, or do they want to create something quick that they can show off to their friends? (and maybe go further if they really enjoy it)