I was thinking, you don't really need blockchains for composability/interoperability, you just need open APIs

permissionless composability, blockchains do provide

but if there were theoretically some non-blockchain tech that just exposed open data, and the end-result product that takes advantage of this data is the same, then the blockchain part would not be necessary for the end product

it costs money to provide that data, which makes it hard to be truly "open"...and then there's the issue of APIs being updated/changing making maintenance hard/time consuming...both i feel like an open consensus mechanism actually is needed?

yeah i guess i moreso meant, the capabilities of a resulting product that uses that data, would technically be the same in theory. i still think blockchains are necessary for the reason you describe, but the end user experience on a product would theoretically not be different