> Should people just not make new languages any more?
They should, but they should understand it's very hard to get widespread adoption when they do. Not impossible, but very hard.
> There was and is in fact abundant tool support for this in Python. The `2to3` script shipped with Python and the corresponding `lib2to3` was part of the standard library through 3.11. The third-party `six` compatibility libraries are still downloaded from PyPI more often than NumPy.
Yes, and even so everyone involved knows the transition took a very long time, required a ton of labor, and was a major headache for many years.
Work on Python 3 began in 2006, and Python 2 wasn't officially sunsetted until 2020 [1]. To put that in perspective, the Python community spend almost as much time migrating to Python 3 as they spent in Python's entire history prior to that point. (Python was 15 in 2006, and it took them 14 years to deprecate Python 2.)
You'll notice too that the easiest changes to automate were the ones that were either lexical (renaming core library methods) or syntactic (print to print()), and the hardest ones involved the change to types of values (strings).
Static types make it much easier to automatically migrate code.