That more than 3300 altcoins that were listed on coingecko in 2021 are already dead again is really very big number. The reason for that was probably that the height of the last bullrun was during 2021 and back then i still remember that crazy meme-coin hype where literally hundreds of meme-coins were created each and every day and of course most of them where dead again within a few days, but a small percentage of them survived longer and made it onto coingecko. Then of course they died too sooner or later.
That being said, i think that there are definitely altcoins out there that are here to stay just as long as Bitcoin itself like Ethereum for example.