I hope that NeoVim will resolve this. The package management systems for new languages like Rust and Elixir are wonderful. NeoVim should follow their example.
It doesn't exist per se, but install pathogen or vundle and you can pretend github is your centralized source, and git your package manager.
The fact that there are multiple package managers is a problem. There should be just one package manager, managed by the core team.
I use pathogen. I just browsed vundle/neobundle/vimplug and and you are right - they are a big improvement over pathogen. I'm gonna migrate to one of them.
But still, IMHO, they can do better. What I see in vundle/neobundle/vimplug isn't as good as systems like NPM/RubyGems/Cargo/Hex.