>>713605539DLSS was the first modern upscaler and people hated it, because it was proprietary and inaccessible even to older Nvidia owners, it relied on specialized hardware which people thought took away from the card's total performance, and it uses machine learning which people despise because word association. And also because DLSS initially looked like shit.
FSR came afterwards as the underdog and people really wanted it to win. Open source, allegedly easier to implement, not reliant on special hardware or ML gimmicks, and was supposed to reach the same image quality as DLSS.
So the hope was FSR would replace DLSS and render it obsolete. People even started trying to wish this into reality before it actually happened, but it never did. FSR never looked good, turns out you need ML and specialized hardware to make image reconstruction techniques look good. So AMD ended up just making their own proprietary, hardware-accelerated ML version of DLSS and called it FSR4, and it ended up being almost as good as DLSS.
So old FSR failed, what is its use case? Well there isn't one. Nvidia users will use DLSS. AMD owners that have access to FSR4 will use FSR4, those who don't and everyone else (GTX users, Intel users) will use XESS because its open model is a less shit version of old FSR. RIP FSR.