Just because a library is safe does not make it good. To the point of the previous poster, you might for instance have an http library which does a lot of unnecessary async work behind the scenes to do a simple synchronous request.

If we all have the attitude "it's good/fast because it's rust" this is not going to lead to a lot of cruft making its way into the ecosystem.

I think if a dependency is a perfectly sealed abstraction, where a complex function is reduced to a simple one with no leakage, then there's no reason not to use it.

Obviously, in the real world, this basically never happens. Performance is one thing that's basically always going to 'leak', so you still get people rewriting stuff in assembly, or making custom asics, because the abstractions that higher level languages offer are not perfect.

In a strongly typed language, with strong safety guarantees, I think there are less ways an abstraction can leak (for instance, by corrupting memory or whatever), so there's a correspondingly lower cost to pulling in a dependency than there would be if you were working in an unsafe language, or a dynamic one.

I also think if performance is the only way in which your dependency leaks implementation details, then it still makes sense to pull in a dependency first, profile, then swap out if necessary.