The chains may still go because seed nodes are active but really most all were forked to print coins for income no matter what was promoted about them or what kind of "development" was done. Some of their values are so bad that they are sub 1 satoshi and even close to one Lsat. These coins are litereally worthless in the current real-world situations no matter their supply. You can literally buy nothing with them without billions of coins and then you have to dump them on an exchange for next to nothing to get BTC to buy anything. Those promoting you can buy things with their coins are just devs selling to devs or devs selling to friends and uneducated persons believing them.
In general, I believe that your reasoning is close to the truth. The cost of most of them is purely speculative and developers are driven by a desire to earn money on seigniorage. On the other hand, I see that the developers of about a dozen of these coins make a significant contribution to the development of CryptoNote protocol and CryptoNight algo family, or have an interesting user case in order to get to know their solutions better and, perhaps, to use them for solving practical problems. It is unfortunate that projects like HOSP or Veronite have closed. But some projects continue to develop. In the development of the idea of the maximum anonymity of the protocol, RyO demonstrates progress, in the development of user software - Loki, BitTube (already traditionally). These are not just forks of Monero, they are developing each in its own direction. Monero, by the way, also still develops. Also take a look of Nerva, that implements the original idea of Satoshi Nakomoto - one computer, one vote. Its truly decentralized and anonymous. Some believe that Haven will succeed in creating a pair of its own market value currency and stablecoin. Thus, I believe that yes, the list cleaning will continue, but some solutions will develop, as the new versions of CryptoNote / Cryptonight (especially Heavy) are extremely cool, as they are truly anonymous.