It doesn't have to be elegant, just popular enough that everyone agrees to standardize on it. The best example I have in mind is the S3: because it's so popular, it's the default API for minio (https://min.io/). Redis is also different enough from every other database yet widespread enough that it's considered a standard, and other projects have started using its API to implement an alternative or a cache.
I also hope that at one point I can just write my code, wrap it behind a simple HTTP API, and give it to some orchestrator that manages everything (monitoring, logs, deployment, TLS, gives me a FS API, manages authentication, ...). I feel like web platforms such as OpenResty (https://openresty.org/en/), Caddy (https://caddyserver.com/) already provide part of it, but can probably go a bit further
I think it does have to have a certain elegance (or better, conceptual integrity), otherwise it won't be able to provide a flexible and understandable interface for handling all the various use cases.
I also hope that at one point I can just write my code, wrap it behind a simple HTTP API, and give it to some orchestrator that manages everything (monitoring, logs, deployment, TLS, gives me a FS API, manages authentication, ...). I feel like web platforms such as OpenResty (https://openresty.org/en/), Caddy (https://caddyserver.com/) already provide part of it, but can probably go a bit further