Agreed, but people have a tendency to do otherwise. At the very least you still have to install the right version of the language. And there are probably an few other tools, linters and such... Next thing you know you've got quite a pile that's not covered by your language's package manager.
I find different languages/ecosystems have different cultures around this. In Java/Maven land it's fairly common to have a self-contained project where all the helpers like linters etc. are set up in Maven so all you need is a vaguely recent JVM and vaguely recent Maven. But there are other ecosystems where people like to throw a bunch of shell scripts etc. in.
When Python comes up as an example of a problematic packaging ecosystem, Java often comes up as an example of it being done right. I think the key is the cultural difference you're pointing to. JVM folk are not tempted to stray from the JVM. Python folk think of Python as a convenient harness for that cumbersome bit of FORTRAN that they can't live without.
I only worked in a Java shop once, but I remember that they looked at me like I was an alien when I proposed that we involve a subprocess written in a different language.
At the time I thought they were insane for writing everything themselves but I've since seen how gnarly packaging can get and now think that they're... less insane.
Agreed, but people have a tendency to do otherwise. At the very least you still have to install the right version of the language. And there are probably an few other tools, linters and such... Next thing you know you've got quite a pile that's not covered by your language's package manager.