Honestly if the theme is just handling the presentation with CSS, and the overall structure can be modified by a user via front end editing, I don't even see much reason that block templates and what not need to exist. I guess maybe it's more inline with your article https://wptavern.com/themes-of-the-future-a-design-framework-and-a-master-theme, but changing the presentation on the page via CSS (and if necessary some JS) is trivial. People used to always reference http://www.csszengarden.com/ as a primary influence of how to style themes, but many themes have just become more and more bloated, and shy away from good design principals in the first place. If authors were forced to design blocks and layouts with just css by only modifying the presentation, and not the structural elements - themes would still have just as much diversity as they do today. Sure there might be some slight exceptions, but I think in those cases, a theme adding additional choices to the editor to dictate the styles they add would be a better solution, similar to block styles that already exist today and are rarely used/implemented by themes. Simple examples being sidebar left, sidebar right, dual sidebars, no sidebar - every theme should have this option in the editor, and a user should be able to easily add or delete the sidebars as they choose. Having a header on top, a sticky header, a header that's fixed on the left or right, etc those things are all trivial and the majority of what theme authors are adding to templates is just unnecessary classes, and checks for customizer controls to change basic things that should already be easily editable no matter what theme a user chooses. For additional flexibility even just having simple hooks to render additional html/class within a "master" template for authors would/should be more than sufficient to achieve any design/development need. Theres of course the developer in me saying I should be able to override anything that I want to still, but if core had controls and ways for users to handle their layout - I could hardly see many use cases where overriding a template would be necessary. Designers focusing on block based components is definitely the future. I guess I do support the "one master theme" approach to an extent, but honestly I am excited to see where Gutenberg takes the future of themes. You're doing a great job of not letting themes be forgotten and bringing awareness. Thanks!