Make the new sidebar / page tree optional

Today you rolled out the new sidebar in Confluence Cloud for me. I now have a second sidebar on the left to switch between spaces, and my page tree looks different.

I'm sure you had reasons to do this. But it has two major drawbacks:

1. It makes working with Confluence considerably slower, because the page tree takes several seconds to load each time (even with a very decent Internet connection).
2. The additional sidebar consumes space on my small screen for something I don't need.

Please provide an option to switch back to the old sidebar / page tree which was much faster, more compact and more configurable!