Agreed. The am not saying eth should do it all. We may need 10-20, maybe 50 blockchains. But definitely no need for 850...
Actually if you're asking for consumer adoption (and remain decentralized) with apps many different networks would be required.
I used ETH as an example because it's proven to be unable to perform during temporary demands on the network (ICOs). Imagine if 200 popular apps were developed (currently there are none that could be considered popular) that were used 24/7. The temporary demand would become a constant. Decentralized networks are 100s if not 1000s of times slower than my cell phone. Yet some people actually think that multiple apps can be run simultaneously on this type of network.
What I am suggesting is that the focus should still be on digital money not apps. The vast majority of consumers don't care how the app works, as long as it doesn't lag in a noticeable way. On a decentralized network a popular app would lag. The vast majority of people care about money.