I think I may not have been clear enough in what I was saying about your point.

Specifically, it seems likely to me that the necessity of tight coupling in new OS development is largely a thing of the past. Advances in hardware have created a greater value for developer resources and a lesser value for system resources, across the board, and that this reduces the value of tight coupling in new system development to the point where it is negligible (except perhaps in concept prototyping).

Yes, there was a time when non-modular solutions made more sense, but they don't really make any sense any longer, for the most part — often even in experimental development, contrary to what I understood of your earlier statements.