Ethereum is only 3 years old.
Every time ETH gets used for an app, it takes down/log jams the network.
I dont think it will be possible to use blockchain to power the web. Slow, unreliable, and expensive.
Ethereum developers are currently working hard on making Ethereum more scalable. It cant definitely power the web anytime soon but its getting better and better. Read about Sharding, Plasma, Raiden etc if you are interested.
When you start talking about offchain ETH solutions or using multiple ETH systems to scale, you are removing the only thing that provides value from Blockchain - Trust.
When an ETH sidechain can get 51% attacked or the entire system is verified through a few centralized locations, you remove the only reason you should use blockchain.
I used to drink the ETH koolaid, I now realize blockchain shouldnt be used for apps.