Another pattern here is to have your edge provider automatically move your compute closer to your backend. Cloudflare released Smart Placement a few months ago to do this exact thing (with surprisingly similar diagrams!) https://blog.cloudflare.com/announcing-workers-smart-placeme...
Author of the simple React example here – Tom says there's a "huge gulf", but forgot to mention there's literally an example[1] of an asynchronous routing and data fetching app linked to in the first section of that page that's a logical progression of the first. (and others have pointed out much more complex examples you can achieve with React if you so wish)
The goal of those small examples is to illustrate that you don't need complex frameworks to achieve server-side rendering with data fetching and routing.
I have no doubt that FastBoot was a huge undertaking, and I think a large part of the reason for that is that it's aiming to fit into a very comprehensive existing framework, with pieces for routing, fetching data, "application instances", etc – there's a lot more work involved in that (for the framework author I mean, not the end user) than there is starting off with just a view library and adding your own pieces around that.
Note the "Dynamic relocation of existing Durable Objects is planned for the future"