[usrusr]

Venice is particularly difficult because of the lack of any in-between. Rome on the other hand can easily fit those millions into an authentic self, because there's so much local life around the tourist hotspots, with a natural blend in between. And tourism is authentic Rome anyways, it would not be Rome without. In Rome tourism is not even a modern invention, back when it was still called "pilgrimage" English and Welsh kings have made that trip between battling Vikings, it's that old.

In smaller Italian towns I have seen AirBnBs that I'd want to grant a "maybe it's not all bad" exception: old town flats that are basically museums to live in. A permanent resident would likely want modernize quite drastically, but tourists interested in the past can be the perfect solution to keep the legacy setup maintained. But that should be easy enough to regulate, plenty of existing cultural heritage protection schemes to tie in with.