I think they've been worse about this w.r.t. tooling (dep comes to mind. The closest thing I can think of along this path for the standard library would be how they've handled errors, and deciding to go their own way instead of adopting dave cheney's pkg/errors[0]

they do definitely seem to have some NIH syndrome at times, but I can't say that as time has progressed that I haven't come to appreciate the decisions they've made that seemed controversial at the time.

[0] https://github.com/pkg/errors