No single exchange can keep up with every new cryptocurrency, so people start creating accounts with all the exchanges, and then start preferring the new ones if they also bring overall site improvements over the incumbents, and eventually dump the incumbents. This is healthy for the cryptocurrency market. If this wouldn't have happened, things could have been a lot worse with centralized exchanges.
I don't know what the "final form" of this ecosystem will be, but I hope it will be something like the internet. Decentralized exchanges essentially being "protocols" like TCP, which link all the cryptocurrencies (servers) and users (clients) with each other, and everyone can "exchange" (connect) one cryptocurrency to another.
But unlike the internet, I hope there will be a much bigger emphasis on P2P connections/transactions, and that we won't sacrifice that just to get a little more performance or more convenience. There will be such more centralized cryptocurrencies, too, just like today's internet continues to have huge walled gardens like Facebook, but hopefully it won't be the majority of them.
A shortage of shitcoins isn't the biggest problem currently for the cryptospace.