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.
Equally (or more?) impressive is the procedurally generated 3D FPS .kkrieger, which weighed a paltry 96KB. 96KB in 2004 was quite impressive, considering that Doom, released a decade prior, was 2.39 MB, and even the original Wolfenstein 3D, released in '92, was 1MB.