I know it didn't escape anyone; I'm explaining the downside to the choices made by the stdlib authors, from my perspective. When performance is a concern, people pick uber/zap.Logger or zerolog. When performance isn't a huge concern, slog is overly complicated and annoying. I believe you understand my complaint.

> I believe you understand my complaint.

I don't, really. If performance is of utmost concern, you're not going to accept the overhead of passing the logger through an interface anyway, so that's moot. A library concerned about performance as a top priority has to pick one and only one.

But if a library has decided that flexibility is more important than raw efficiency, then the interface is already defined.

    zaplogger.Info("Calling third-party library")
    thirdparty.Call(slog.New(zaplogger)) // Logs whatever the package logs to zaplogger
    zaplogger.Info("Called third-party library")

Your library should just take a *slog.Logger, and using *slog.Logger is an orthogonal choice to zap/zerolog/whatever. Those compete with slog.TextHandler or slog.JSONHandler, and sure, if you’re performance sensitive don’t pick them. In my newer projects I use zap under the hood with an application-facing *slog.Logger through go.uber.org/zap/exp/zapslog just fine (actually further locked down with my own interface so that coworkers can’t go crazy, but that’s beside the point). Your bespoke interface, or that standard interface you want isn’t going to be any more performant than going through slog.Handler interface anyway.