The real problem with the idea of a decentralised exchange is not the technology, its the users.
Users do not care about decentralisation at all. The only thing they care about is convenience, fees, speed and security. DEX has great security, but fees will always be higher and speed will always be slower.
Correct, users don't care.
Plus, trade speed will be the critical problem that will prevent any DEX from seeing high volume, especially in the future.
I've spent quite a lot of time looking at ways to achieve high frequency trading (HFT) that is both secure and reliable (trades don't go missing, no "queue jumping"), and I don't think its possible to get < 5 second easily without some form of semi-centralization. When you compare traditional HFT exchanges such as the NYSE and others which are able to process trades sub-millisecond, well, our decentralized counterparts are never going to be able to compete as a serious alternative.
The fastest I've been able to get trades in our DEX with sufficient reliability is about 10 seconds, but that comes with quite a bit of overhead across the board in terms of bandwidth, processing and other costs.
Don't take this the wrong way, as I like you and your eMunie project, but I don't get this statement. You claim eMunie can process way more TPS than Bitshares, yet you can't get trades to settle on your DEX in less than 10 seconds? That doesn't make sense to me. Bitshares settles trades in less than 4 seconds reliably. In fact, 4 seconds is the maximum amount of time and it usually takes around 2 seconds, but it does depend on when you click the confirmation but in relation to when the last block was produced. I suggest trying Bitshares' DEX. I think you will be impressed with the speed of settlement.
Also, I don't think anyone expects DEXs (at least as the technology is today) to realistically compete with the NYSE or other large HFT exchanges. I only expect them to compete with cryptocurrency exchanges in the near to immediate future. You can however trade stocks and commodities on Bitshares which is a benefit compared to most cryptocurrency exchanges.