Chainlink's model has hardly proven itself, even if the marketcap could lead one to guess otherwise.

Node participation is permissioned and the economical model has not even started to be tested: queries are free and nodes are paid through inflation (i.e. from token holders). The whole model of trust in oracles depends on incentives, so in reality nothing much at all has been proven.

I have pretty much given hope in seeing concrete progress from SmartContract at this point. They're now hyping off-chain computation while the simple decentralized JSON query usecase is still vaporware. If you're interested in this area, you could look towards The Graph, as they attack essentially the same fundamental problem and are launching an incentivized testnet with actual economic incentives[1].

[1]: https://thegraph.com/testnet

You can get decentralized world opinion from a trusted source of truth. The reality is that blockchain guarantees break down right exactly at the point a single element of trust enters the system. This invalidates the entire guarantee and therefore the costs associated with blockchain are purely superfluous.

Uh, s/you can/you can't.