Perhaps done in an effort to suppress user score review bombing.
Ghost of Tsushima MC

According to a new report by Paul Tassi, via Forbes, Metacritic seems to be doing away with allowing users to submit scores on games until at least a day after release. Tassi notes that user scores for the just released Ghost of Tsushima only has critical scores posted for the game. The user scores are currently showing a message that user reviews will be permitted starting July 18 at 12PM (PT).

The message where the user score average would typically appear displays the following message to visitors.

Please spend some time playing the game.

Come back to review it starting at 12:00pm PST on July 18.
As the game came out at midnight on Friday, July 17, it seems as though the delay is roughly 36 hours from the time of a game's official launch time. This is quite the change from a system that used to allow users to submit their totally legitimate scores mere seconds after the game was released on a platform.

Tassi speculates, and I have to echo his suspicions, that this was done in light of the recent review bombing that happened with The Last of Us Part 2. Internet trolls, bigots, and the like flocked to sites like Metacritic to review bomb the game down to a 3/10 right when the game was released. Some of those reviews flat out had gibberish for the written portion.

The initial issue was that there were thousands of reviews that came out almost instantly on the game’s release, when it was physically impossible for players to have played more than a couple hours, given that the length of the story was more like 20-30 hours. These people were submitting reviews based on things like story leaks, streamer playthroughs or just getting to a single story beat near the beginning and rushing off to write an angry review. This new 36-hour hold seems to be fighting against that directly.
Sadly, saving the world from the horror that are unfiltered user scores by merely a day may not be enough. The wait period on user scores at Metacritic should be extended closer to a week. It is a lifetime in terms of the Internet, which may prove to be enough to dissuade mass efforts to review bomb a newly game for whatever reason. An additional point of deterrence would be to have a system wherein you must prove that you own the game before you can submit a review. This could be accomplished through linking your Metacritic account to your gaming accounts on PlayStation, Xbox, Steam, Epic Games Store, and the like. There are plenty of sites that already do this very thing.