Valve has taken measures to update Steam's reviews platform so that user reviews will now "better describe the current customer experience in games." Essentially, changes were made to which reviews are displayed by default -- the most recent reviews will show up first so you can get a better idea of how the game in question plays currently rather than how it did in the past.
There's also a new "Recent review score" that will appear on a game's page that offers a calculation of review scores within the past 30 days, if there are enough reviews to provide it. The game must also have been on Steam for at least 45 days.
All of this information is collected on the game page with a summary tab to check the most recent helpful reviews, a checkbox to tick to disclose that a game was received for free, and the ability to see any review no matter what language it was posted in. You can see a full log of changes as well as Valve's explanations here, but this should just make things easier to wade through if you take Steam reviews or any reviews for that matter seriously.