That's critics...a lot of his stans aren't feeling Kendrick this time around, lots of casual fans aren't feeling this album and that's from my observation. I don't think there's any doubt that this album alienated some of his fans. Personally, I really like the album and think it's better than good kid, M.a.a.d. City.
Even It Was Written had good reviews, 4 Mics from The Source, nearly perfect reviews from the Chicago Tribune and LA Times, and A- review from Entertainment Weekly, 4 stars from AllMusic, etc.
It Was Written had "good" reviews but nothing comparable to Illmatic and the general consensus within the Hip Hop community has been that IWW has been rather underrated until recent years when younger artists and fans have been vocal about its influence. The sound that Nas went with and the Escobar persona were divisive.
To the contrary TPAB has Universal acclaim, it's going to debut at number 1 next week, Kendrick as far as alienating fans, other than trolls on these boards, I've seen an otherwise positive response in real life. People coming into the store looking for the physical all week. If it reaches the sales of GKMC then I dont see how, along with the critical acclaim, anybody can compare the reception of this album to the delayed appreciation of IWW