I look at that as a feature. I already have applications I'm comfortable with for browsing and selecting media. I just want a new rectangle to play that media on.
The fact that anyone on my Wifi can access it with their phone, instantly, with nothing to install is a magical experience.
> 3. Music sounds terrible through it. It lacks an optical audio out port so it just uses the TVs speakers which are obviously not great.
HDMI Audio Return addresses that. If your TV and receiver support that (I think most do?), then audio will flow from the Chromecast into your TV and back up the TV's HDMI cable into the receiver.
My Chromecast plays audio through the speakers hooked up to my receiver just fine.
> Am I missing where I can stream my Android device's OS on the screen?
Maybe Chrome for Android supports that? I don't think there's OS level support for Chromecast.
> There are many, many things the Chromecast can't do.
Sure, a boat can't do many of the things an airplane can, and vice versa. They're different devices with very different user experiences.