In Grové’s tests, Unity took 15.4 seconds to compile scripts, while Godot Engine took just 0.31 seconds, which is a significant gap. This is likely due to Unity’s standard use of the compiled language C#, whereas Godot uses its interpreted in-house language GDScript, allowing for much faster iteration times.
Both C# and GDScript are (typically) compiled to bytecode, so they are probably more similar than they are different when it comes to the compilation step. (C# does get compiled to native machine code by the .NET runtime, the GDScript bytecode is likely still running in an optimized interpreter.) There is no excuse why Unity should be taking that long to compile its scripts. Certainly that's not a failure of the language used.