And of course, standard library APIs age with time. Perl and Python are good examples. Both ship with packages that were really good in their day, but have long since been superceded by community-created tools. But the core has to keep shipping the old thing for backwards compat and the maintainers are reluctant to add yet another package that does the same thing.
Dependencies have their downsides, but being able to assemble the best of what's out there rather than relying on the best of what was available at some point in the past has a lot of advantages too. Languages with good dependency management seem like the best possible option.
Go's refusal to embrace this is a huge pain point. Dep is a decent start, but without a community actually doing things like releases, changelogs, and all the other things that go into a solid ecosystem, it's a half measure at best.