The problem isn’t that we don’t have a “process”.
the procedure for tag deprecation through the tag proposal process so far didn’t have automatic retagging included, it leads to the tag being labeled “deprecated” in the wiki. Judging from taghistory, there are sometimes also some larger retagging efforts after this labeling, but they are not part of the tag proposal process (often they are not discussed or announced and every case would have to be individually assessed).