It has about as much handcrafted content as Skyrim if you count all settlements, crafted-quests, dungeons, etc. Just because it has a ton of procedural content with a ton more random missions than Skyrim doesn't mean it has less handcrafted.
I understand why some people say it feels like Starfield has little to no content because they swim (or fact travel) in an ocean of procedurally-generated stuff.
For me, each playthrough I'm discovering at least a handful of big new things I missed the previous playthrough.
To get to brass tacks, estimates have been showing Starfield has approximately 400-500 named quests. Skyrim vanilla has 274.
So if you think it won't last as long as Skyrim because you think nobody likes it, that's defensible from the Mixed reviews. But it's not due to lack of content but (arguably, because I like it) quality of content.
How does a loading screen "prolong" playtime when the alternative is going or flying everywhere in real time?
Game is short. People complain.
Game is long. People complain.
Game makes you stare at five hour space travel. People complain.
Game gives you fast travel. People complain.
Game takes you by the hand. People complain.
Game forces exploration. People complain.
Quantitatively, Starfield simply has more hand-crafted content than Skyrim. More and bigger cities/settlements, hand-crafted dungeons, and handcrafted quests. In the map-size cases, it's only slightly more, but in terms of quests, Starfield has about as many hand-crafted quests as Skyrim and Fallout 4 combined.
Now, if you don't enjoy exploring in Starfield, you won't find a lot of those quests (same as Skyrim). Heck, if you don't enjoy the quests themselves at all, that's a thing too. There's a neat hand-crafted quest around every corner... if you're not so bored you just rush the main story. I for one really liked the Neon Street Gang quests and (haven't finished it yet) the Crucible quest chain. Both of them I completely missed in my first playthrough because the game didn't hold my hand to find them.