C# compiles and JITs incredibly fast and has generics. F# has the same generics and compiles far slower. The reason isn't compile times. (Especially since one impl of generics is just generating code, which is cheap.)

IIRC the reasons on the list were the standard tradeoffs of memory space and so on. Do they emit specialized versions for each function, or not, and so on. Again, stuff that's working fine in other platforms.