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.
I’m probably thinking yeah. I mean, you could probably get it to run on HDD, but I’m thinking that if Bethesda created this game similar to their others, there is a boat load of cells per planet/in space and it would be way more than what you would load into the RAM, so SSD will significantly reduce load times.
Kinda sorta required if you want to stream assets from storage, an approach taken by many modern games. Might not be absolutely necessary depending on your setup / game settings. BG3 also said SSD required but there's a "Slow HDD Mode" in the settings anyway, which I believe just shifts more of the streaming burden to RAM/VRAM. If you played on a HDD without enabling it, I guess you'd expect to see inconsistent pop-in as individual assets try to stream in faster than your storage can read. But playing with it enabled might also cause performance drop if your RAM/VRAM was already close to full utilization with the setting disabled
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.
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.
It's going to depend on a lot of things, like how much system and video RAM you have, what you have running in the background, etc. I think it could be viable running on HDD under good conditions, but I remember needing to install games like Planetside 2 to SSD to stop the stuttering as you move around the map.