DEX are already quite good for crypto-crypto exchanges. But they continue with the problem that the issue to trade fiat to Bitcoin has not been fully solved. It is still more risky to use them to buy or sell Bitcoin than a CEX:
- If you buy, you may get accused to not having sent the money because it's not easy to prove hat you did. You may also not be comfortable to reveal your account data to someone you don't know. You also may get tainted Bitcoins (depending on the exchange mechanism).
- If you sell, you may also get tricked, or you may get money from dubious sources like stolen bank accounts (this is partly solvable, but only if you avoid new accounts as a seller. So as a buyer you'd have to wait a month or so to accrue enough trust ...).
Yes, there is Bisq, but for a safe operation you require a Bitcoin deposit. There is Bisq2's "easy" mode but that is basically a good ol' reputation based exchange market, like the one in this forum.
I don't know if this is fully solvable, or if there have been new ideas to solve these issues in the last years.
Don't want to disappoint you, but the truth is bitcoin has opened the era of decentralization and DEX has also had 16 years to develop. But so far, it has not been able to develop and compete with CEX.
This is quite an unfair comparison because electronic trading platforms, which operate in the same way than CEXes, exist for about 50 years now. Apart from that, CEXes only need a crypto deposit/withdraw and hot/cold storage infrastructure. The challenges for DEXes are much more significant and crypto-specific.