You may not be seeing many Doom (or Do4m or whatever) reviews up for the game’s 13 May release, because, by the accounts of several reviewers, keys will not be going out until launch.
The NeoGaf thread on the subject references Jim Sterling’s podcast, in which he does indeed confirm that Bethesda won’t be sending him anything until release day. According to the PR email read out as part of that show, it sounds like Bethesda’s reasoning is that servers for multiplayer and ‘SnapMap’ editing stuff won’t be available until launch, so people would only be reviewing the single player campaign.
Other reviewers chime in throughout the thread to say that, yes, they’ve heard or been told the same.
Not sure that’s the greatest explanation in the world. It’s obviously in Bethesda’s power when the servers are switched on, and having early code to at least play the campaign would be useful for critics. However, it also doesn’t necessarily mean Doom is going to automatically be awful. The same happened with Wolfenstein: The New Order and that turned out alright. But, as someone who always advocates for early code (for obvious, job-related reasons), this kind of situation is generally unhelpful.