you can do this in SharePoint today (i.e. put all members into Read Only permission bucket)
An error occurred while saving the commentAnonymous commented
I get the idea is to allow quick collaboration but there are so many scenarios where read-only is going to be desired (presenting HR docs to staff as one example). I would ask is Microsoft trying to move away from traditional (classic) team sites? If so then having more granular ability to control permissions is going to be important to meet various use cases.