Many music streaming services have no API:s, and those that do have (to the best of my knowledge) worse API:s than Spotify. I'm very grateful that they provide any means of integration. However, that doesn't get them a free pass to get on as high a horse as they try.
Now for the part where I gripe. They recently created a dedicated site shaming Apple for, in part, not exposing the same internal API:s/abilities/possibilities to Spotify as they did to their own and perhaps some other third party apps. That's pretty rich.
Where is the protocol specification or available-for-everyone library for creating a Spotify Connect endpoint? Locked behind Hardware Partner Applications, NDA:s, Evaluation Agreements, New Product Applications, Device Certifications and Distribution Agreements (yes, all of those, according to their own site). Talk about subjectiveness and forcing people to jump through a thousand hoops -- like they accuse Apple of. "and final approvals for commercial usage will always be left up to the discretion of Spotify and its partners". Three cheers for transparency and a level playing field.
Where is the web API support for folders, a feature that you clearly use yourself in the desktop application? The web API has been launched for years without folder support. This feature is completely private and unavailable to others. In the GitHub issue about it that they closed with WONTFIX the motivation was in part that folder support didn't fit well into their REST API, which is some of the weakest sauce I've had in quite some time. I used your C library and I know that you implemented folders as "begin" and "end" markers in the huge, flat playlist list. Perhaps you regret that design decision, but if that makes it an expensive API call then rate limit it accordingly. Make it subject to change as you evolve. Just don't close it off and keep it private for your own apps.
Yes, I'm annoyed. I've been a loyal customer, user, developer and fan for almost a decade. They get to expose or not expose any API they like, that's their prerogative. But what they don't get to do is gripe about the subjectivity and closed off-ness of others if they don't practise what they preach. I hate hypocrisy.
If you've read this far, I apologize for spouting bile. Time to sleep, probably.