The dashboard shows the top 25 critics ranked by number of reviews, as well as a time chart for each critic.
You can also switch the view to show these charts for reviewed games instead of critics.
Verdict: On the one hand, there is a clear positive trend as more and more reviews for stadia games are getting written.
On the other hand, the total number of reviews is still very low. Hence, only 10 of the 189 available games (5%) have a valid Metascore (which requires at least 4 critic reviews per game).
The Explorer tab gives you a timetable of the various reviews by the top 25 critics.
Hovering on a review data point reveals more details, the overall rating and the summary of the review in the tooltip.
➤ Link to the Stadia Metacritic Monitor
Have Fun with the Data!