Everquest 2 is such a game. It is basically dead in terms of attracting new players, but people who love playing it have been keeping the parent company afloat for a while. IIRC, WoW and EQ2 came out at the same time. I can easily see Blizzard having the same fate in the not too distant future.
In f2p or bolted on cash shops like FFXIV I'm always wondering, should I buy some mtx? I don't really want to encourage them too much. I don't know what is reasonable to spend to keep the game afloat, I don't want to feel like a leech, but I really have no interest in cosmetics. I don't know if buying or not buying sends a stronger signal to them to spend more effort on mtx rather than the game - sometimes it just seems like all roads lead that way.
FFXI is in a similar state to EQ2 I'd guess, it only has the monthly sub but a really hardcore base who's still there (or dips their toes back in like I did for a bit) after all these years. It still gets minor monthly updates and probably has a nice ROI for the effort.
The article does say that Shadowlands and WoW Classic carried the torch for revenue. One is old-Blizzard quality I guess, the other pretty much as expected for a new WoW expansion. People are going to buy it. Whether or not they stick around is another story. It does note that they did not confirm if subscription numbers are rising or not in WoW (modern).