Whether one holds Olivia accountable or not, the "House" IS the ultimate prick, the something that causes all of the bad stuff that happens to the Crain family. Which is one reason that I dislike the house was allowed to stand in the end. The final episode even painted the house (and its ghosts) in a sympathetic light. Fuck that. It should have been burnt down.
Even the Dudleys, after Nellie's death, should have gone "OKAY FUCK THIS WE CAN'T LET THIS HOUSE KILL MORE PEOPLE". Doesn't matter that they didn't know for sure whether Nellie committed suicide or not. They know the house is bad both on the preternatural- and natural level. Enough is enough.
The Dudleys had already enjoyed so many years together with their non-aging ghost daughter. Know when it's time to kill the beast FFS.
The ending was definitely the weakest part of the show for me. That said, I am surprised it wasn't an even weaker ending. 99% of the time, horror movies and shows jump the shark at the end. Here they didn't so much jump the shark as they danced around a puddle of piranhas.