By now it is probably no longer news to many: GNOME Shell moved from GJS’ own custom imports system to standard JavaScript modules (ESM).
Extensions that target older GNOME versions will not work in GNOME 45. Likewise, extensions that are adapted to work with GNOME 45 will not work in older versions.
You can still support more than one GNOME version, but you will have to upload different versions to extensions.gnome.org for pre- and post-45 support.
Please file bugs with your favorite extensions or have a friendly conversation with your extension writers so that we can help minimize the impact of this change. Ideally, you could help with the port and provide a pull or merge request to help maintainers.
Um, you’re like more than a decade too late to ask this question. Javascript is pretty much everywhere now, whether you like it or not.
For the record, I dislike it as well - not the language itself mind you, but the fact that they’re using it to make bloated desktop apps and desktop UX. Long gone are the days when devs cared about performance, sometimes going as far as writing code in ASM to get the most out of paltry hardware.
Nowadays, even a $25 computer like the Raspberry Pi has enough computing resources to run bloated JS apps, so no one really cares any more, except for old fogies like us who grew up using entire operating systems that fit on a single floppy disk.