This is actually a shutdown that makes sense to me: why would it need a separate app/website? I don't think it was actually really useful for most people:

* As a standalone gaming streaming service, I don't think it ever had the potential to dethrone Twitch, for various reasons already said by other commenter

* On the other hand, if you are a heavy YouTube user, it doesn't add anything: almost all features are available in the main YouTube app.

Basically, it always seemed redundant to me.