I am actually working on my own language, and getting something better than Go is actually not that difficult!
The hard part about making a language is creating the stdlib and tooling and support for the language, but actually creating a language itself that has more features and better features than go can be done by a single person in a few months or a year probably, depending on how much experience they have.
Generics specifically are a great example here. A single person can implement a language with go-level generics fairly easily.
