I'm not sure why it's considered the dumbest thing ever; it's clear that it works. Every new technology will have growing pains, nvidia was the one to take it on (foolishly I would say). A lot of developers may not be interested in supporting a feature that is RTX only. But that doesn't mean a third party company couldn't come along and do the exact same thing using DirectML and supporting all GPUs.
I don't see DLSS as being any more expensive or less cost effective than other solutions. You build the game as you see fit, you let the AI company do the work. You take their model and you integrate it back into your own engine add it to the tail end of your pipeline. Effort on behalf the developer is quite minimal.
Solving this problem via as a general problem sounds trivial, but there will be edge cases that will require refinement on all titles. That will also still be on nvidia to solve. But as they get better at solving these problems they can apply this model forward to the next title and the next title.