I don't see any nominal growth in the volume of Dex and the problem with DEX is its not user friendly along with not appropriate for fiat trades so its still not under the alternative list of centralized exchange but I hope in future the things may change and more people will look into the DEX.
Also the exchange has to upgrade atleast better UI so the users will feel the ease of usage.
Decentralized exchange has a fiat pair too, not only coin/coin. Also the UI/UX isn't that bad, it's still user friendly, people just don't want to learn about it. The first time when they use centralized exchange, they also don't have any idea how to trade their coins and willing to learn to explore the site. So there's no excuse to not use decentralized exchange due to not friendly UI.
People then trust decentralized exchanges more than they trust centralized exchanges.
Wrong, you must compare the trading volume in centralized exchange and decentralized exchange first, without any data you're just talking non sense.