For some, a few days of GDScript usage. For others, after they convert their bottlenecks into C++.
UE’s blueprints are much(!) slower than native code, but they’re still an incredible tool in the toolbox. GDScript is kind of the same; it’s covering a critical role of non-performance-sensitive glue.
That said, I’d really like to see Value Types added, as well as these sorts of heap allocations addressed in Godot 4 at some point.