> As a non-developer who has only gone as far as "hello world" in Go, I'm baffled by the idea that the log/slog thing is new - that seems like an absolutely basic language feature.

Then you'd be even more surprised when you learn that the vast majority of languages do not have standard logging library in core.

Most have one or few common libraries that community developed instead, but they are not in stdlib, and if stdlib has one it's usually very simple one (Go had standard logger interface that was too simple for example)