If you don't do that, you get the python 2 to 3 transition. Which is still going on.
PHP did drop some stuff between 5 and 7, but all of it had been marked deprecated for some time prior (often years).
> Javascript has made progress too.
To be clear, this is what I was saying when I called upon it as an analog.
I also think that both JS and PHP get a lot of flak for maintaining backwards compat as far back as they do. You can run a lot of webapps (frontend and backend) from 10-20 years back in modern PHP and browsers which is pretty amazing. I'd like them to have a modern mode (like the proposed p++/<?php2020 and modules for JS) we should still acknowledge that maintaining compat that far back is not easy.