You have raised an interesting and necessary question, but is everything the way you write? If we talk about centralized exchanges, then we cannot say that they are all not reliable or work somehow incorrectly, because it all started with them and not all centralized crypto exchanges are reliable or scammers. As for decentralized exchanges, they are certainly based on decentralized processes, but this does not prevent fraudsters from deceiving users. Moreover, the word DEX itself has recently been used by many as a bait for investment and it is far from the fact that there is anything at all connected with decentralization. I have personally seen many different platforms, both CEX and DEX, and I cannot say that someone is better and someone is worse. I can say one thing that some and others have a number of problems that need to be addressed.