10 years ago was 2014. What python code are you talking about? Deprecated, sure, and some things have been taken out of the standard distribution because nobody would maintain it(or there were reasons to not maintain it.) 2->3 conversion was 16 years ago.
While I still do run into 2.7 code, even for 3 dependencies are the problem. You always use a library of some kind and that library could use a new python feature. You could pin it but then other scripts that need the new version break. And that is if you could even easily find the module and version. Just this week I helped someone troubleshoot a bug they've been trying to fix for weeks/months and it was just a matter of the library code being too new for 3.6. It's an ever growing planned mess.
