Twitter and Tumblr are operating on skeleton crews but are able to make changes.

Craigslist is still around even though it hasn’t changed much since the '90’s.

There is an entire industry of companies that buy old MMO’S and maintain them at a low cost for a few remaining players.

Southwest Airlines still runs ticketing on a Windows 95 server.

I think you’ll see more companies accept managed decline as a business strategy.