Yeah sorry it's been a while, I just remembered he praised the game to heaven.
Of course there are objective reviews for "art". There a several icendents that have to be achieved, like emotional attachment to the characters, a story line that come to a head on very dramatic and emotional events and so on, while Witcher 3 feels like work, it's exhausting to search for Ciri, just asking around for her and do those ones how know about hey favours to gather informations, or the quest where you accompany Ciri through Novigrad for like 30-40 Minutes, to say good bye to old firend who helped her out. It's just plain boring and you're asking yourself the whole time why the heck you even do this, almost the whole Mainstory plays like that, it's not exciting at all.
And there are the bugs, it's not my opinion that the inventory is quit messy when first playing the game (one get used to it though), it's not my opinion that there are crashes, glitches, exploits bad design decisions like putty candles everywhere you can loot and interact with stuff, or that your hose is doing a fullstop every few meters in specific areas.
All these things can be rated and finally judged. And Witcher 3 did a lot of mistakes. It's still a freaking good game and I'm enjoying it a lot. But it's simply not a 10/10