My experience with DEXs is limited, I've used mostly CEX and OTC, so I may be somewhat wrong, however, imho CEXs are still viable in quite a number of situations:
* Established day traders are using them so I expect better volumes, for example.
* Some (and I think they're many) prefer CEX because they are more newbie-friendly and fool proof.
* If you want for example to sell for fiat, a CEX may have connections with local banks and you have better chances to get your money than from random traders.

I've been using for example Binance when they had their card. It was pretty safe and convenient to sell coins like that.