Here's the thing though, at least to me. Going by the Steam Hardware Survey 67% of users use 1920x1080 resolution, and GPUs have been capable of 1080p60 gaming for several years now, even the most popular card on the survey, the 5 year old GTX 1060, can do it with little to no detail compromises on most games.
By using any subsampling-upscaling filter or feature, be it DLSS, FSR, or an inbuilt subsampling feature which some games have, you're making a detail compromise, for FPS purposes. When nVidia and AMD were caught doing this in their drivers, I remember there was a massive outcry from all the reputable tech sites, including TomsHardware, at how underhanded it was, but now in 2021 it's a desired feature to cut quality in the name of FPS?
So to say FSR is a feature which benefits 100% of the userbase is a stretch. For laptops and IGPs certainly it's a benefit given the weaker power of them, and it's much akin to how this generation of consoles use dynamic resolution to maintain FPS, but for discrete card PC users...