MakeGenericMethod with custom type

I made my own Type class for some reason, it works with most cases except MakeGenericMethod. Seems that MakeGenericMethod does not support custom types.

Is it possible to use generics with my type system?

Here's what I tried. https://dotnetfiddle.net/F92t8Z

And, here's .Net implementation https://github.com/dotnet/coreclr/blob/a64cb0a41a4ebeb4a61b8b0f1f2eeeff8dd539c9/src/System.Private.CoreLib/src/System/Reflection/RuntimeMethodInfo.cs#L625-L633