I'm a bit confused by that take. Fallout 4's character progression works differently than Skyrim, the weapon and armor modification is completely different due to the gathering and breakdown of materials, and the way those populate the world dramatically changes the gameplay loop, the world itself was totally different, there was settlement construction, voiced protagonist, I mean shit, even the pure fact that the main combat gameplay was "finally enjoyable" gunplay makes the moment to moment gameplay fundamentally different from magic, arrows, and swords.
You can extremely whittle that down to "Skyrim with guns" but aside from being open world power fantasies with certain bethesda trappings like Radiant quests and AI schedules it's absolutely not just a skin of paint on Skyrim, those games scratch a different itch.
If anything Starfield is absolutely taking a lot from those Fallout 4 specific innovations such as settlement construction expanding to ship construction and weapon and armor modification through materials coming along.