kind of surprised Swift didn't launch with this by default, built in-house
Everyone in the Go community more or less uses the same Go modules support built into the SDK binary, much like how almost the entire DotNet community uses the NuGet package manager support built into the dotnet SDK binary. There are no extra dependencies to grab your project dependencies and build it.
My experiences in those langauges is that there is so much less debate over tooling, and people just get work done. No one in DotNet is waging an equivelent holy war about Gradle vs Maven etc...
I'm all for choices, but the languages who have made package management a first class citizen in their SDKs tend to be the languages I've enjoyed working in the most. I think package management tooling is a critical piece of developer ergonomics.
People used to joke a lot about how JS has a new framework every week, but I feel that way about Python build tooling! I've now had to use uv, poetry, pipenv, hatch...
I wasn't arguing against Swift needing a default package manager, I agree with that. Just the examples you picked to compare with are odd in context. You could compare Swift to its contemporaries like Rust or Zig and come to the same conclusion.