Once upon a time the barrier was the existance of VMT tables and method dispatch.
GC use can be optimized in high level languages with support for value types (which are still missing in Java, though) and it is not like every game needs to be the next Fortnight.
Only tangentially related to your comment, Fortnite is based on UE4 so it does use garbage collection. And it has caused framerate/hitching issues as recently as a year ago according to an Epic developer.
My point being that everyone evaluates programming languages for writing games as if they would be doing a AAA hit, when they will actually be doing a minesweeper clone.
