Many Golang projects I see in the wild will import a number of dependencies with significant feature overlap with sections of the standard library, or even be intended as a replacement for them. So it seems that having an expansive stdlib isn’t sufficient to avoid deep dependency trees, it probably helps to some degree but it’s definitely not a panacea.
The problem is that the UNIX shell model got very successful and is now also used on other platforms with poor package management, so all the language-level packaging system were created instead. But those did not learn from the lessons of Linux distributions. Cargo is particularly bad.
They're not either, every one of these projects contains a gigantic vendor/ folder full of unmaintained libraries, modified so much that keeping up with the latest changes is impossible so they're stuck with whatever version they copied back in 2009.
there's nothing stopping you from using python from 2009 except why would you want to do that to yourself - but the same strategy applies. the reference python implementation is written in C, after all.