DEXex are gradually coming up to fill the gap for high fee, but at the moment, traders and investors alike will still continue to patronize centralized exchanges for some reasons, which decentralized exchanges cannot for now fulfill. Coinbase has high traffic caused by traders and investors on their exchange, so it is likely that they would have generated such huge amount of money.
There are too many Dex's and all of them have very low liquidity - you can place an order and wait a week for it to be filled.
Rationally some Dex's ought to close and the remaining ought to consolidate, but that doesn't seem to be happening.
how long your order will be filled will depend on how much liquidity in the market place of your token. For your information, if I have ever experienced my order didn't even get filled for more than two months of waiting.
Those dexs are operating under their own company and we know that so many dapps protocol has already made to provide a better system for dex to build its dapps in the various protocol.
That's impossible for them to be consolidated from one to each other.
So many dexs make the volume in the market have divided even more to the various new dexs. I remember some dexs are getting less and less size of volume every day.
It looks like the dex is getting overloaded.