I understand your point. But, if I take your example of mount and blade. If it’s starts off strong with 50 hours of fun, that’s a win in my book. But yes, in this regard steam ratings fail, because of binary recommend or not recommend voting. On the other hand, you can see how many hours did the user that posted a review played, so you can kinda make your own decision.
Also, I would like to add that games like dwarf fortress, rimworld, factorio and similar, all start of fun, if you’re into this genre….at least for me, they did. Thinking back, I think I never experienced playing a game for X hours having a horrible time, and somewhere in the middle changing my mind. At least from the gameplay standpoint. Maybe sometimes story had some unexpected bump in quality (thank god), but not really core gameplay.
Overall, I agree with you, 2 hours is too little for a complete review of a video game. But these are user reviews that can be helpful as well. For an example, for someone who hasn’t that much time to invest in a game to get to the good part. Professional reviewers (or people who have themselves as professional) should play the game for a suitable amount of time, before making an informed review.