Recently I was writing a custom static site generator for my website. I started with python and yaml using the pyyaml lib. After two months (don't laugh, I wasn't writing this generator all this time; i had a break) I tested if everything I wrote previously was warking. Pyyaml came at me screaming that they deprecated something and I shouldn't use it, otherwise the feds will get me.
Let's go several months earlier still. I was learning Python, using Debian Stretch which has Python 3.5 installed. The book I was learning from used Python 3.7. When I got to a point it became clear that 3.5 lacks a few things which are needed to continue learning Python according to the book. So I compiled Python 3.7, set up virtualenv with it and... The code I had previously written stopped working. With a version bump from 3.5 -> 3.7? That's a minor version change. And now 3.5 was expecting at one point to have a string path passed as an argument, and 3.7 was expecting a pathlib path. That was trivial to fix in case of a small example, but I would dread using such a thing for anything big and then having to debug what exactly broke between different (minor!) versions of Python or its libraries.
These new hip tools seem to have a backwards-compatibility issue.
I eventually settled on using XSLT and a couple really short shell scripts (which all fit on my screen at the same time) and I don't expect them to break in the next two decades.
However, XML is still a pain and I would prefer just using S-expressions and Lisp[1]. It's just that for now my only experience with them is writing things for Emacs and I would like to learn Scheme/CommonLisp to do anything outside of Emacs with Lisp.
[1] https://sites.google.com/site/steveyegge2/the-emacs-problem