As one of the perpetrators of gengo, we focused on simple, fast, and dirty. We wanted something a little higher level than Go AST to deal with types (for gen), and we knew we wanted to gen a ton of code.

Some of the Kube code generation would not be solved by generics (or at least, not obviously) such as our API conversion logic which defines arbitrary transforms between structs and generates the rest. The others (proto, defaulting, etc) would.