It could be argued that 3GB RAM is not exactly flaship material when heading into 2016.
While there is nothing massively bad about the Nexus 6P, there certainly is something ugly. The Qualcomm Snapdragon 810. Regardless of your stance on this processor and whether or not you do believe that it is a problematic processor that overheats, it is one which has now become somewhat cursed. The Snapdragon 810 is just not a good processor to have in a phone right now. Many had hoped the next generation Snapdragon 820 would be included, but it was too early.