I am not the devil's advocate. I am just right.
Well first, they did not have 8 episodes to watch. The screeners sent out only had 5 episodes. Second, this is how the vast majority of television reviews work. Even on streaming. They review an episode, maybe 3 a lot of the time. For streaming shows it is somewhere between 4 episodes and a little over half the season. And that is what the season's review is based off of. Unless you think people have been reviewing the entire season for shows on their premiere date in October, when it finishes up in May. I still remember when Luke Cage received all those rave reviews for the first half of it's first season, when all the, "WTF" was in the second half.
Was it stupid? Yep. Was it unprofessional? Sure. All they had to do is say they watched two episodes, and thought it sucked. But that wasn't the question. You asked why they would say a show is completely crap based off two episodes. If I watched two random episodes of Batwoman this season, I'd tell you the same thing. And guess what, I'd be right. If I watched two random episodes of Watchmen, I'd tell you it's awesome. And again, I'd be right.
I have only seen the first episode. Did not like it much. But I have heard it gets better, and I am curious to see if I like it more by the end. I didn't like the pilot much for Penny Dreadful, and I ended up loving it. But it isn't like the Witcher is reviewing overly well. It is split down the middle on RT. So it isn't like EW is vastly out of step. Also it is super disingenuous to compare an episode of a show, to a chapter in a book. Especially when you consider that is how they decided stuff like the Emmys.
The first season of Punisher did not go all that well with critics. I didn't complain. I don't usually complain about critics, no matter their views. As you know, they are all individual opinions.