It's not that hard to explain. Upscalers (today) are good for getting *most* of the visual fidelity at a higher resolution, specifically, so you can actually get that acceptable response time while also getting most of the visuals.
Frame generation is, functionally, for...watching the games, rather than playing them? They will *never* actually improve game responsiveness, only degrade it. Since most monitors now, and *all* video cards for that last 6 years or so, support VRR, the argument that frame gen is there so you can hit the max refresh of your monitor *to avoid tearing* is largely moot. It's great for those watching a presentation of gameplay. It never actually improves it for the one playing it.