The ideology that everything has to be completely cryptoeconomic and trustless is hugely overblown. It's good that Ethereum eliminates the central trusted third party for the base layer, but then you are free to be flexible with how you define trust in your applications. Obviously you can't "cryptographically verify" a complex topic like health; you need to delegate decisions to intelligent actors.

If you're delegating decisions to intelligent actors, why not delegate to intelligent actors who make a payment app that's denominated in dollars and includes none of the complexity of Ethereum?

Because for some reason I enjoy using a smart contract blockchain as the platform for my interactions. That might be for example because I also want the ability to use the service with a multi-signature wallet... or because I have been locked out of PayPal for political reasons or because I am a vendor of erotic literature (https://www.engadget.com/2015/12/02/paypal-square-and-big-ba...)... or because I want the ability to pay in a number of cryptographic tokens... and so on.

Ethereum has value even if it doesn't involve somehow replacing all real world services with cryptographically proven algorithms. Interfacing smart contracts with external actors is a really interesting frontier; see for example Vinay Gupta's latest venture, Mattereum. http://internetofagreements.com

A program could compare the output of a gene sequencing reaction against a known database to verify that such and such fish matches what's on the label. But then you have to trust whoever is loading your fish samples into the gene sequencer.

And the fish samples that are loaded into the sequencer are not the same as the ones in circulating supply.

Basically the way people are thinking about blockchain business models right now, require everyone to migrate to the new platform for it to really work.

Both migrate and participate earnestly with no attempts at dishonesty. Most discussion of smart contracts or sales where abuse wasn't either ignored or differed to the same courts and trusted third parties everyone currently relies on, at which point the discussion goes from revolutionary change to minor incremental improvements.