Wait til you discover that the web version of YTM can't chromecast. Yep, Google's own music product can't communicate with Google's own music player product.

The "solution" is to cast the tab. Which means lower bitrate, no music controls, and if you cast to a display device, the whole tab screencasts etc.

I guess it's because nobody important uses the web anymore? Or something?

(Disclaimer: I work at Google. But not on YTM. Most Googlers I know have switched to Spotify, including myself.)