As games change and get updated, reviews must also reflect that, and Valve agrees.
Valve makes changes to Steam reviews to make them more relevant
Valve has made some major changes to the way Steam reviews are being curated in order to better reflect the status of the games in their current form.
The new rules are not in effect, and Valve had a lot to share about the new direction. Previously, review scores and exposure was done in such a way that you couldn't tell if they applied to the current version or were simply referring to launch issues that have since been fixed.
Valve is changing this in two ways. Firstly, recent reviews will be more prominently visible, and review pages will now default to the most recent, helpful reviews.
Second, the way scores are calculated is also changing. Review scores used to be based on an average of all reviews. Now, review pages will show a 'Recent' review score that only takes into account reviews posted in the past 30 days (assuming the game has been available for at least 45 days). Both scores will remain visible.
Other smaller changes have also been made, such as the addition a 'Summary' tab, which only features helpful and recent reviews. Valve added an option for reviewers to disclose if they received a the game for free, too.
To see the new additions, just head over to any game's store page.