A lot of "reviewing" suffers from the same problem that informs much of Internet comment, people know so little about what they're talking about but think they're experts. (Dunning Kruger Syndrome)
Browsing/skimming instead of actually reading is another big problem. I suppose it derives from the DKS as well, people thinking they know a lot more than they do. And being lazy, in this case.
Perhaps reviews-as-advertisements are influenced by games themselves. How many board game boxes have you looked at that tell you little about the game, but a lot about the story, even though the story may not have anything to do with how the game is actually played (typical in Eurostyle)? I haven't looked at the backs of enough RPGs lately to know if it's the same there, but I know some RPGs are sold on the basis of the story rather than the game.
As for being impressed, student-age people seem to work hard to not be impressed (or at least, pretend not to be impressed) by ANYthing. Part of the Zeitgeist, I get. OTOH you get those to whom most anything is "amazing".
In video games, the usual view is that reviews hardly make a difference to sales. It's watching others play (online, usually) that really makes a difference. I think it's notable that (as reported on ENWorld) such a large proportion of new D&Ders first experienced the game by watching others play online.
Yes, you need to say whether you were provided a review copy. And probably, who you played it with (not their names, but what kind of players, whether they were the creators, that kind of thing).
I don't think you can call a game "review" a review if you haven't played. You can know a game pretty well without playing it, if you read the rules, if you have lots of experience, and if you talk with others who have played. That's how I learn about board games in detail. But I don't review on that basis. Readers expect a review to be based on immediate experience.
Formal reviews have a higher "bar" than user reviews in comments. We expect more from a formal review, we don't expect much from comments!