This game will run fine on a 2080, by the time it's been fully patched and optimised by the modding community. Honestly, can't wait till 2025 when I'll be able to play the finished game.
Starfield was originally planned to be released 2 years ago. But when Microsoft took over they gave Bethesda another 2 year development time, which they mainly used for polishing if you believe the talk about that. In that case it's not surprising that the requirements are more comparable to games of 2 years ago instead of current releases.
HDDs have been holding back what you can do in open worlds for a while. It (and the PS5 specifically having an extra emphasis on hardware decompression to amp it up further) was the thing I was most excited about for current gen consoles. There were a lot of rumors that PS4 Spider-Man had to cap web slinging speed to allow the HDD to keep up, and we'll see what the movement options are in Starfield and how ships work (unless we know already and I haven't seen it), but even the jet pack boost thing could seriously strain loads in denser areas if it allows enough movement to feel good in opener spaces.
With the way they reused, dynamically loaded assets before and tried to keep world seamless, they'd probably load\unload parts of these 125 Gb a lot, with this 16 Gb RAM requirement no less. They test it with SSD and make it so it doesn't have microstutter and loading problems on their target machine. Or, god forbid, loading screens when walking outside, like it was in TES3; or TES4 banning levitation and loading complex cities as different locations that won't work in a space sim etc etc. BethSoft had many problems with it already. I doubt it'd refuse to work, but if they build their game around it, the result is unpredictable. Bet, it'd load low-res LOD textures and only then replace them with okay ones. That'd probably ruin the spaceship landing – one of the, possibly, most demanding and visually sweet parts of the game. It looking great is their baseline here.
It will likely still have loading times hidden behind unskippable animations. (See the door opening animation in the gameplay reveal.) You're going to need an SSD to make that work.