The "Pages" option is confusing (and I don't talk about it's layout with "User icon" displayed everywhere where this is not the author icon that is available for anonymous users whereas they can't see it when reading a page), the sidebar customization with the page tree and space shortcuts that could be seen on all pages including the "overview" page was better. Moreover I don't like the fact when you navigate in child pages, you have to click on "<- Pages" then "Overview" to get back to the space home page, a page we generally customize to help users in navigating by adding some comments and explanation (this is not possible with the "Pages" page you provided). Getting back to the home space requires too many clicks and as we can't click anymore on the "space name" that is above this "<- Pages" link because it now displays a drop down list, navigation is very very complicated. I could click on top of the page as the space name is also displayed in the form "<space name> / ... / <my page>" but if the space name is too long, the display is ugly and does not mean anything. And I can also mention the space history located above the "<- Pages" option does not work for anonymous users, all they have is "All spaces", no history, meaning it is more complicated for anonymous users to navigate between spaces.
With the option you provided to allow us to add space shortcuts in the sidebar, I can't anymore create a common page that can be included in all sidebars, that was very easy then to add a shortcut to all my documentation spaces, now it's a pain as I have to update all spaces one by one.
Conclusion: I do not need the "Pages" option, please give us back the sidebar customization option you removed, display the page tree on all pages, display the header/footer on all pages including the overview page, add more customization in your new releases and stop removing features your customers use !
Page tree is back to space navigation sidebar as of May 2018, removing Pages menu item. Other sidebar items can be turned on/off using the Edit pencil icon at bottom right of the sidebar by space admin.