I read something today for work, something I wouldn't have otherwise read except for a work requirement, etc... I was probably above the "mediocre" level, more of a B level. I could skew it either way, talk it up and explain why it is ok, or look for every flaw in it.
I guess what I would say: no imaginative flair, no "brilliance" in evidence. Quotes dull (or wrong) things from other critics. A few obvious mistakes, but very few. He quotes someone else who talks about someone's reaction to an imminent historical event, something that hadn't happened yet, and that presumably nobody would know would happen. I would have to track down the original quote to see what the first critic said.
Whenever I talk about something like this I make sure I alter some identifying details to make it unidentifiable. If I say I read something today, it was a year ago. If I say it was a year ago, it was today. If I say he, I mean she, etc...