Thanks for your comment! Yes, I ignored the VPS angle simply for ease of narrative, but you're right. I also updated the shared album example to hopefully better explain why this is hard from a technical and UX perspective.

As to the "convince people to switch" angle, I think the benefits of data interoperability would be pretty significant and eventually lead people to switch to providers that have that or would likely incentivize providers like Apple to implement that into their products.

Ideally, no one would have to switch and everything would just get better.

I like the vision though and would love to see it become reality, if just to have the alternative.