Let’s try and read the comment more charitably: most clients do not offer a good solution for this either, making the protocol less appealing than it might otherwise be.
Ok then we can just phrase it as there's no standard way to sync RSS subs across apps. Point is its a clear user frustration with no easy solve.
Fever API is implemented in many apps.
Cross platform applications and web based readers exist. It is easily solved using one of those.