I was referring to driver-side optimizations, though, not DLSS. That's something that can only be added by Bethesda themselves (mods excluded).
One can surmise that they only added FSR 2.0 due to its being an AMD partnership title, but I suspect there's a lot more to it than that. It's not clear at what exact point in the development cycle of Starfield that versions for other platforms were dropped (if any were ever being done), but Microsoft finally acquired Bethesda in March 2021 -- that's a pretty short amount of time after the Xbox Series X/S platforms were officially launched.
It's also around the same time that AMD launched FSR 2.0 and it seems to me that the decision to focus solely on an upscaling system that could be employed on the Xbox and every PC that could run the game was made around that period, too (perhaps no more than 12 months later).
The AMD-Bethesda partnership wasn't announced until just a few months ago but such agreements take a while to put together and set in stone, by which time I suspect Bethesda had already finalized the engine and wasn't going to alter it after that point. It's possible that AMD genuinely didn't know if the devs were going to utilize other techniques (its marketing division isn't the best out there), hence the silence when initially questioned about it.
Modders have shown how easy it is to add DLSS and Frame Generation to the game, so the lack of support for them (and XeSS) shows that the 'blame' can't really be attributed to AMD, Nvidia, et al -- this is a decision by Bethesda (and possibly Microsoft).
I honestly believe that this was just about prioritising FSR because that
is in the agreement. Bethesda probably thought "We can release it earlier with only FSR and people will be able to survive for however many weeks it takes for us to issue a DLSS patch because FSR still works on GeForce cards.". I honestly doubt that AMD and Bethesda expected a bunch of GeForce-owning conspiracy theorists to come up with these insane ideas.
I took a quick look around and, sure enough, the nVidia Reddit says this:
Bethesda will be adding DLSS support in a future update for Starfield
I even said that I hoped that these rumours were false because it would make no sense and it would make both AMD and Bethesda look terrible. The crazy reactions from some people really puzzled me because it was like they
wanted it to be true just so they'd have something to be mad at. Considering all the other crap that Bethesda has had to deal with as far as Starfield is concerned, I can't say that I'm surprised they put DLSS on the back-burner in favour of fixing issues that actually plagued people and ruined their experience.
Sure, FSR may not look as good as DLSS but it's funny because I had been playing for more than a day before I even realised that it was on by default. I was trying to tweak the graphical settings to see what I could get. As it turns out, Starfield is CPU-bound to 57-62FPS at 4K Ultra Native with an R7-5800X3D and RX 7900 XTX because no reduction in graphical settings had any FPS improvement whatsoever (not even 4K Medium with FSR!). If I hadn't gone in to tweak the settings, I never would've known that FSR was on just through gameplay, which impressed the hell out of me (although it was at 4K).
Game crashes and bugs that prevent mission completion are issues that really do ruin a gamer's experience. Show me a person who claims that using FSR instead of DLSS completely ruins their gaming experience and I'll show you a living brain-donor who probably says the same BS about ray-tracing.

