Wrong. In fact if SE or any other business follows that mindset they will very quickly run themselves into the ground.
In every content creation field from novels, to music cds, and to games, each new release has even more opportunity to attract new followers than the previous one. In fact there's actually business strategies that revolve around this because it causes a chain effect: if people like your latest product, they're far more likely to go back and also purchase your older ones and binge on what you've made (like the few folks on here that have paid for FFXI after playing XIV just to see how things are different).
MMOs (and video games in general) are surprisingly similar in that vein. You have to remember that not everyone (in fact I'd argue the majority now) really doesn't care about "Keeping up with the Jones" like end game raiders that hop from game to game to follow what's new. There are indeed still people joining WoW, Guild Wars 2, FFXIV, and dozens of older F2P MMOs (hell, people are still joining Runescape and Mabinogi for crying out loud) for the first time despite their age. Companies have to keep appealing to new players over time, otherwise they run the risk of not replenishing players who do leave. Which makes populations lower and queues longer, empty worlds, and thus driving the die hard vets who remained to leave. Look at what happened to the Gilgamesh server during the server lockouts. That will be the entire game if they suddenly stop making an effort to appeal to new players.
A good business never stops appealing to new people. It's striking that balance with older fans/customers that's the hard part.
