Check out riko [1]. It was developed to programmatically replicate Yahoo Pipes (without the UI). But as it stands, I'm pretty sure it can do most of what google feeds does.

[1] https://github.com/nerevu/riko

(full disclosure: I'm the lead dev.)

Writing a system that (correctly) interprets the zillion flavors of "RSS" out there and presents them with a common API is non-trivial. An 80% solution is pretty easy, and a 90% solution isn't that hard, but a near-100% solution will take you into some very dark and ugly places.

I don't know of any service that does this as well as the Google Feed API did. If someone else does, please share.

Well, start the service, state you use RSS library X and that you will keep it updated and send people over to it for bug reports and contributions.

Ah but RSS is a standard, so where's the problem? One method to recode them all surely?

I jest, I'm the author of http://www.weegeeks.com - I know only TOO well, how there is no such thing as a 'standard' RSS feed... (sigh)

So yeah, I get your point.

Superfeedr https://blog.superfeedr.com/google-feeds-api-welcome/