However the core language way of dealing with enums for example is extremely weak. It's common to have a typed enum on a struct. When parsing the struct, random string (or whatever the alias is) values sneak in and the only thing you can do is validate.

They’re convenient but error-prone. I think everyone who wrote a decent amount of Go had that malformed, misspelled, or misnamed (“db” vs “sql”) tag at some point.