It is very difficult for many altcoins that do not have good economic model to exist in the future. Some altcoins are not modelable for blockchain. In other words, it is unnecessary to use tokens or blockchain to do the project. There's a lot of unnecessary projects like this.

There are many projects that copy one another. Those with clones here have very little chance of survival. For example, every month a lot of masternode coins comes out.

It should not be a surprise that many mainstream altcoins like Ethereum, NEO, ZEC, XLM, and Litecoin etc. continue their existence.