I was just in Paris and visited several places in Italy a couple of years ago. I saw both locals and tourists wearing everything you just said not to. Things have changed a lot, and this is not the 1950s. I don’t promote anyone dressing like a slob, but you don’t have to dress the way you’ve said. Tourists cannot really blend in…locals can always tell who the tourists are. If one is going to a fancy restaurant or a church, many of those do have a dress code and it would be wise to research what that is before goin to them. Otherwise, dressing for the weather, comfort, and for the activities is important. There’s no way most ladies will be comfortable wearing ballet flats to tour the city, unless they want blisters developing. White sneakers are very much in style in many countries. You absolutely can wear sneakers in museums, churches, many concerts, and nearly every other site one is likely to visit. Rude and obnoxious behaviors will get one targeted faster than anything a person wears. I appreciate your trying to get folks to think about what they wear, but a lot of this info is dated and doesn’t ring true.
I’ve watched many videos from Alvin Hub (bushman prank) and yes many people dress nicely but many dress showing skin or wear yoga pants. I think dressing respectfully crosses borders.