For example… let’s say you have just plain search-replace and no smart tools. You need to update github.com/abc/def to github.com/abc/def/v2. This is a search-replace operation.
This only happens when packages publish breaking changes. The minor version is stored in go.mod.
gofmt -w -r '"github.com/abc/def" -> "github.com/abc/def/v2"' .
That won't do subpackages though.
Every language starts the way you describe, then needs are added.
What is complex versioning? In Go, you specify a minimum minor version, and breaking changes change the package name & import path (or they’re supposed to). Why would I want complex versioning? The underlying problem that versioning solves is complicated, but that doesn’t mean you benefit from a complex versioning scheme.