Decentralized exchanges need to take over centralized exchanges in the future, going fully decentralized is what makes more sense around crypto, centralized exchanges can be controlled by the law and government, I heard court is asking users data from centralized exchanges too, just imagine if all exchanges in crypto space are all DEXs, I know that DEX has its flaws too but it's safer than centralized exchanges
Yes, now the DEX has grown and improved a lot over itself 3 years ago. However, it can only pass CEX if the problem of fees and transaction speed improves, and it is possible that the coming ETH 2.0 will solve this problem.
High transaction fees and speed isn't the only problem that DEX have, the major problem are lack of Liquidity, Volumes and bad interface, very confusing for newbies to use, interface and dashboard must be users friendly just like most centralized exchanges, I doubt that DEX will take over centralized exchanges for few years more but nothing is impossible
No worries, DEXs will become more and more important over time. Uniswap, for example, profited a lot of the last Defi hype and still has a nice and easy to use UI in my opinion. Once they release v3 they will implement even more features.