Empirically, I think you'll find that Go code generators are
bad compilers. Go codegen isn't written with AST transformations and quasi-quote libraries. A macro system would be an opportunity for the Go compiler to take responsibility for the the tooling around metaprogramming; in the absence of that, we have a fragmented ecosystem where everyone is always reinventing a minimal, hacked-together version of the wheel so that they can get on with building the thing they actually need.
Frankly, an official Go codegen library would solve pretty much all my complaints, but the only difference between that and a macro system is compiler integration.