People are only still playing Skyrim (and morrowind, or even daggerfall) because they aren't happy with what bethesda has produced since then. Bad sign for Starfield!
There is truth to that. But thats only part of the reason. You forgot to include Fallout 4 btw. It at any time on Steam has 15k plus people playing. The other reason, the main reason, is mods. Fallout 76 was a join effort between Bethesda, Arkane, and Zenimax Online and iD. Anyways, yeah, 76 sucked. I suppose it is playable now. I played a bit but grew increasingly disgusted with the monetization.
Starfield will be a success. It will be easily moddable. And people will play it for years. I don't believe it will have quite the same staying power as Elder Scrolls and Fallout because I don't believe they will make a sequel anytime soon if at all. Its back to Elder Scrolls and Fallout before Todd calls it quits.