Sadly, to build a community around a coin, you'd still need staunch supporters right? And most, if not all, would try and use the money to advertise it so in the end, it falls to the factor of, again, the problem of money.
Besides the lack of promotion and lack of volume, DEX also the trustless system which need require deeper knowledge to control it, this is what the newcomers avoid the platform, plus the UI/UX that are not familiar in the eyes.
It's strange how much time it takes for people to get familiar with changes and accept them. The first step was making them go from a completely centralized fiat system to semi-decentralized Bitcoin. Now they're slowly getting ready for a completely decentralized system with anonymous cryptocurrencies and DEX.
I'm only afraid that it will take another 20 years and we'll be old farts unable to fully enjoy it when it comes.