I think the advantages of decentralized exchanges is the new project can list the token with more easier. Different with centralized exchanges, listing in DEX is more cheaper and sometimes free charge and centralized exchanges always requiring huge listing fee and not many project can afford it.
indeed it is true of the costs to be registered in a decentralized exchange cheaper there are even some that are free. but such exchanges are not chosen and trusted by investors. most of those who register in small exchanges are only project scams and don't intend to develop their projects.