I hear you! This particular improvement is so exciting because it actually allows us to avoid a lot of complexity in making new settings, special cases and conditions and to accomodate for simple requests. Also, it is a result of the work being done for a few custom implementations we're working on now. 

Just think about this simple request: someone wants a login page with nothing but a login form, in the middle pf the page, not stretched to the entire page width. Currently it's not really possible to do - you can create a page without a header or footer, but then you have to choose layout which specifies sections with proportional width, without absolute constrains. So, we have to make a half-page login form with some placeholder text/image on the other side, hide the other side on mobile, etc. With these macros, we can just create a block with a container that has specified width constrains, centre it, insert login form macros and job is done. 

I feel that it should give us shortcuts to servicing lots of custom requests without overcomplicating the system settings.