(In English - sorry!).
I think this discussion needs to be had more widely than just within the German community. I don’t think it would be sensible for the German community to revert changes or come up with a specific approach in Germany alone.
I note b-unicycling has responded to a changeset comment saying there was no mechanical edit but there clearly has been a mass edit.
My personal opinion: I don’t think a full reversion (i.e. to delete archaeological_site=* tags and replace with site_type=*) is sensible but perhaps restoring site_type=* alongside archaeological_site=* might be useful. To note: I voted to approve this new key but there was no mention in the proposal of a mass edit.