What was ruined because it became popular?

Reddit top voted comments...

The Sorapiss Lake in Italy. Used to be a beautiful calm place, now it reaches 2000 tourists per day. thanks Instagram

Dumpster diving. People leave the place a complete mess afterwards and now so many stores and restaurants lock up their dumpsters at night

Goodwill and other thrift stores.
Even my local GW in a wealthier neighborhood has particle board trash ticketed for twice the original purchase price new.
I remember the good old days when you could actually find decent lightly used furniture, decorations, kitchenware and odd knacks for cheap.

Mount Everest. From what I understand, it's become a bad idea littered with empty oxygen bottles, corpses, and turds.
And the rest of the planet is all downhill from there.

My favorite local swimming holes.
Pre internet/cell phone days I could cruise up to my local abandoned rail bridge or mountain creek with my friends all summer every day and never really see anyone.
Now you can't find parking.

YikYak
On my campus it was a lot of funny, original jokes nut it got taken over by a bunch of complainers. Got really depressing too with a lot of repeat jokes sprinkled in.

Quora.
The quality of the content has gone down significantly in the past few years. Ever since the Facebook crowd started pouring in it became a junkyard of cliche questions.

The housing market in (name your trendy city)

Several dog breeds. Every time a breed gets overproduced the animals suffer a decline in quality.