If a stranger wants to run anything on their system, alone, never touching anything else and never coming into contact, whatever. But I very much look forward to a world where "Python" == "Python 3" precisely because it keeps impacting me. If I use a package that continues to use python2, I have to keep a python2 installation on my system (complete with some set of modules). Meanwhile, I can use the very latest, 100% maintained GCC or Clang to compile any C standard version, so I don't think that's a good comparison.
I would hesitate to call them at fault per se, but yes I think if such an option has been provided, particularly at a fine-grained level so that modules could be moved over piecemeal, we would not have had nearly as much difficulty with this transition. On the one hand, removing some of the pressure would have meant that the old versions stayed around longer, but if the system genuinely works and doesn't hold up the evolution of the overall project, I'm not sure that I see a problem with that.
