It can be good to reduce chrome and focus on content, and have minimal UI's but there's a limit. Your UI still has to be discoverable, and intuitive. With everything hidden away it's unfriendly, particularly for new users.
I don't understand how decreasing the contrast between content and chrome helps you "focus" on content. The older design screenshot has better content clarity than the current design.
Sure, but why can't we have both? Sensible, usable defaults for new users, configurable views for everyone else. I'd like a version of Pages where I can turn off the toolbar, turn off the title bar, fullscreen the remaining window and focus purely on the document. That really shouldn't be difficult.