Not all platforms are equal, and apps have to be specifically coded for each platforms APIs/requirements (e.g. WebOS, RokuOS, Android, Android TV, FireTV, Tizen, Windows, etc) which requires different code.
Most service providers try to make their apps look the same as much as possible on different platforms with a UI layer that gets loaded at runtime by the platform layer of the app.
I doubt they are punishing Roku users, its more likely they arent adequately maintaining the app/incompetence (happens all the time with apps/app updates).
I dont know if all SXM users are experiencing the problem, but its been reported by other users as well (see previous post link).
Roku may already have contacted SXM about it , but you can inform Roku of the issue with SXM: Highlight the SXM app, use Options (*), Give us feedback/Could not login or authenticate
I actually recommend you get the FireTV devices (I recommend the FS4K) for this very situation - you need multiple streaming platforms for issues of app availability/compatibility/functionality (you never know when a bad firmware/software/app update is going to render an app unusable for a time).