What an excellent quote from a dev back in 2015:
If someone asked me what Path of Exile's greatest strength was, I'd answer with just one word: depth. The breadth of choice and volume of interesting interactions between skills, supports, passives and items are what differentiates Path of Exile from other games, and what keeps players coming back over and over again. Path of Exile's greatest weakness, on the other hand? Complexity.>
Even now, I completely agree. They know it's the reason their game is great and the reason it is niche.