Unfortunately, I don’t think there’s an option to turn the in-game canvas back on yet. I like the new version, but the old one was working fine on my end and I kinda miss having the option to access canvas in-game too.
I partly made the assumption about “launch stability or due to popular demand” due to this thread from the Q&A category which got a lot of attention: Explicit Uploads. Just to clarify, I don’t have any insight into the devs’ reasoning, it was simply an educated guess 
Maybe we’ll hear about what made this the obvious choice for them in one of the future Brainstorm with Kjun? 