As much fun as this have been I have decided to stop development on this plugin. It has been an uphill battle for quite some time now, and I feel the final nail in the coffin has been set. The LocalApi has been shut down, and I am currently rate-limited from using the WebApi (So it wouldnt be able to handle the amount of traffic we need for real-time info). To be perfectly honest I haven't used Rainmeter actively in a few years, so continuing the development has been 100% for you guys (which I have truly enjoyed ).
As i have considered other implementations pretty much every time something has broken, I finally decided to dive into the Chromium Embedded Framework that Spotify is built on. Turns out I'm not the first guy to get that idea, and this is where the good news comes in. There is already a working plugin for this. Worked for me with the Monstercat visualizer out of the box.
Download at https://github.com/khanhas/Spicetify.
Thank you for your feedback and help all this time, hope I see you around.