The article kinda dances around this point, but I think the largest reason "old games never die" is simply the old games mentioned were the good ones of their generation. Similar to the lindy effect[0] where shows that had been around a while were likely to stay around a while longer. The are the games good enough for people to host fan servers and make mods, and behind each good game there is a lot of forgotten stuf…
Even the successful games of today are likely to die eventually. Ubisoft's The Crew was relatively successful, but they shut down the servers and made the game unplayable. Now they're talking about at least adding an "offline mode" but core features of the game would still be unavailable to the customers who bought it.
The difference with games today is that many are designed to require a connection to company servers - and those servers cannot be self-hosted. Eventually it won't be profitable for the company to continue running those servers and they'll shut them down. Unless companies are forced to provide an EOL plan that allows customers to continue playing the games they bought (could be self-hosted servers, open source, patching out the server requirement, etc), modern games will continue to die at an increasing rate.