That would mean Illustrator doesn't use your document profile.
I have tested this on 24.0.1 and it works as expected for me.
What might have happened:
- the document profile is corrupt (can you open it from the Finder?)
- Illustrator has somehow nuked itself or at least its preferences (when did you last restart the computer - did you rebuild the preferences already?)
- the folder has issues read/write, permission, a bad day, headaches, whatever
How to reset prferences: https://helpx.adobe.com/de/illustrator/using/setting-preferences.html (try the "rename folder"method first)
Cool, it works again but different. After renaming Prefs and restarting Illustrator the templates didn't appear in the new doc dialogue. I just opened them manually for the folder "New document profiles" and after that they apeared again in the new dialogue. Also the color swatches are there again.
I think you're right. Somehow AI didn't really sue my templates. But why.... I just realized that there is file named "Adobe Illustrator Prefs.err" in this folder …\Adobe\Adobe Illustrator 24 Settings\de_DE\x64. I guess an error happened here one day.
Anyway: Many thanks!