I'm hoping it will get there eventually. The backup mechanism on Android has improved a fair bit from what it was at the start. It used to be that you had to have the backup file in the correct magic path before starting Signal for the first time. Now at least there is a dialog and you can pick the file whenever.

The usability issues for non-tech people have been getting less and less in the past years which is keeping my hopes up.

Agreed. I understand they are reticent to allow backups for security reasons - but they're treating their users like idiots by doing this. Some people will have threat models where the ability to retain/export messages is worth the risk this may introduce. Let people make their own decisions.