In all honesty it's not really changed things that much, it's just accelerated the time it takes for a place to be trashed from 3 months to 1 month. You can't really blame YouTube for it all, online is online, google indexes and links everything. If you post a place online at all, anywhere, you have to accept that you're contributing to its downfall, whatever your personal ethos and ethics may be. The irony is that all those who bitch about the demise of urbex and the rise of urban tourism are the very people who contributed to and participated in it's evolution in the first place. The whole thing started with us. Those in glass houses shouldn't throw stones, as they say.
On the whole, urban exploration (in both senses of the word) died and became urban tourism many (at least 10) years ago, arguably urban exploration has never really existed at all, it's just an edgy phrase people used to make themselves sound cool (also reflecting YouTubers attitudes now, oh the irony). There's really nothing special about it, there's barely any exploration involved, you're just looking around mouldy old buildings like many before you have and many after you will. That doesn't stop it being interesting though, and it's simply human nature to want to do things that you find interesting.