That is not a python specific problem.
yes it is. python is a very good example of how that whole thing can really get out of hand. i doubt other software programming languages have this issue to that degree whatsoever other than Rust of course since the OP mentioned it kind of has that issue 
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This can't happen because it would limit development and discourage any new developers from creating any new packages.
clearly there is a need for centralization to some degree. i mean if bitcoin core just let anyone put their code into it without serious peer review and evaluation of whether it was really necessary do you think there would be a bitcoin?Quote
It's true that there are sometimes more than one package doing the same thing but most of the times they are different in some ways, for example one could perform better, have some additional functionality, or better API, etc.
no it's not that at all. vitalik's bitcoin package was forked over 800 times. do we know what the difference is between them all? and do we even know which one we're running when we install bitcoin on python? 
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In the end, the choice is up to the developer using those packages. They have to do some research into the respective repository and see how mature the project is before using the package.
well, and that's the part of the problem. using one metric to get a handle on another metric. maturity doesn't equal no bugs necessarily. they need some better way to guarantee people the packages run correctly such as certification process that they give to particular packages. one for each type. one for bitcoin for example. then if someone wanted to change that package, it would have to go through a peer review process like linux kernel.