Decentralized exchanges are the ones needed most, we are trading decentralized coins in centralized exchanges 
but no worry we have great dex OAX developing
but no worry we have great dex OAX developingNo, we don't need exchanges, centralized or decentralized.
If we're going to really move to a cryptocurrency we must start using cryptos directly.
Right now exchanges have gone far from what they were supposed to be and ended up as a stock market where everything is priced in fiat.
We only need places where people that haven't yet bought coins can buy them, and A LOT of places where people can spend their coins without having to sell them for fiat before.
I definitely agree that we need all that, places where people can spend their coins directly, merchants accepting crypto without looking for payment processors, etc. But how are we going to get there? Bitcoin has been widely known for at least 5 years, since the Mt.Gox times. And did we get any further from there? You can't force Bitcoin's use in the economy. With that said, truly decentralized exchanges or rather wallets which provide the decentralized exchange features may be a small step in the right direction, which we should make quite a few till we get where we want to be.
Actually we know about different crypto and pros and cons. TOP one crypto (Bitcoin) limited supply is about to get a bit more limited but still there's a lot of variability in the process thus there will always be plenty of bitcoin to go around. Most cryptocurrency needs now a days is a detailed explanation of the supply and digital scarcity.