I remember using etherdelta a lot in 2018 there were a lot of erc20 coin airdrops. Idex was no less famous in that year. I know that in 2020 many people sell eec20 tokens on uniswap. Uniswap is getting more and more popular because of its huge airdrop. 1 user can get 1000 dollars.
It's the option of those who see Uniswap as a good exchange. If your token is listed there, then sell it there.
But with the vast of exchanges, it's very common to have them with erc20 tokens. You need to search for the supporting exchanges that have your token. Searching them will help you suit what you think is the best exchange for that token.