I don’t get the opposition as this is not some minor new feature a them supports or not (like having customizer options or not). This is a major shift and completely different approach to themes, and “promoting” (if one can even call it that) of Block-Theme seems a total valid option. It is rather only a filter then a promotion in my opinion. If one wants to use WordPress 6.0 and beyond with FSE, one would need to find the appropriate themes easily. That is it. Nothing more or less.