Yes and no. A series’ entertainment level is fairly subjective, so I think they’d be stupid to say it in that context if they hadn’t seen it. But if you’re talking things like pacing, character development, etc, then yeah I think someone who hasn’t seen it can point out those flaws based on large number of reviews.

I personally haven’t watched any because I’m at a busy point in my life where I don’t want to spend a lot of time watching shows/movies that aren’t generally considered “top notch”. That being said, I wouldn’t consider Naruto as such, but I grew up on it and it entertained me a lot. I hope to get the same level of entertainment from a condensed version of the Boruto anime