IDEX is the best DEX for all ERC20 tokens but a DEX that covers most of the coins is still not there. Two years is a long time in crypto world so some new DEXes will rise to fullfil this market void.
IDEX forced all of users to did KYC and after the implementation of KYC and there's no a lot of people have been using idex again. I used idex last year and i never try to use it again right now.
Uniswap has come with a better features compared with idex. People can also earn passive income from uniswap too.
As long as the progress will always be running and the best dex will never be replaced by new dex