This is spot on. I found myself using Fly for a project because it was super easy, not because I needed edge compute. TBH it's still actually unclear to me who needs edge compute? What apps require this sort of infra? It's not 99% of web apps right?
I still think that in the next pendulum swing we'll end up with edge computing and (smaller) self-hosted backends. Everything old is new again, and we haven't entirely recreated Akamai from first principles yet.
One of the big benefits of edge compute is that it’s geographically distributed. Doesn’t make a big impact across the US, but globally a lot of nations have specific data laws, so it’s important to host data in the required nation. Keep customer data in its nation of origin, but have a single control plane and platform for ever data center.
It is going to be apps that provide rich experiences that need to do a lot of server communication to deliver them. I am thinking of things like collaborative whiteboards, for example. If 2 people are in Europe, working on the same whiteboard, then it should be low latency. The edge nodes will be near each other (or next to each other).
Personally I see this as a 'why not, if it works' type thing.
Sure you don't need it for 99% of usecases, but if it just works using familiar architectures then it is also strictly better for 99% of usecases so you might as well, and people will naturally want it.
That 'familiar architectures' part is the hard bit, though.
But it isn't better in 99% of use cases. Lots of use cases are rendering an API response or HTML page that involves multiple database requests. Therefore the distance between database and app server is more important than the distance between the client and the app server.
Edge compute can be helpful for static or quite cachable content. But often this is handled as well or nearly as well by a caching CDN.
So that leaves a few cases where edge compute is useful. Where you are globally distributing the data itself (and ideally moving the data around as your users travel or move) which is incredibly rare and expensive to build, and when you need pure computation that needs no request to your backend and if 50ms of latency is important for a pure computation most of the time you can just move it to the client. In my experience these tend to be rare. I would estimate that edge compute is actually helpful for 1-5% of projects, not 99%.
