IDK, I think 10 hours is plenty for any game, and 2 hours is enough for most. By two hours, you’ve likely discovered the core gameplay loop and seen how it handles progression, and by 10 hours you’ve seen whether that core gameplay loop changes throughout the game.
I don’t like negative reviews for games when they’ve spent double the time HLTB gives for a playthrough. I don’t expect to play much more than “main + extras” on any game, so any review that’s expecting content beyond that just isn’t useful for me.
The thing is, with big RPGs like Starfield, you decide what your core gameplay loop is. It has multiple.
So if you find out the core gameplay loop is not for you after 2 hours, you can just try an other one.
But it doesn’t excel at any of those play styles. It’s the classic case of “Jack of all trades, master of none.”
I guess it’s fine if it’s the only game you play, but if you have choice, I don’t see why you’d pick Starfield over other games you could get. It’s kind of like the cult around Minecraft, you can play pretty much any style you want with mods (e.g. soccer, Pokemon, roller coaster, etc), but every style is done much better in a standalone game.
So I give Starfield an 8/10 or a B, it’s pretty good, but it doesn’t really stand out in any particular way.