I enjoyed the finale, Emmerson and Amy were superb, they sold the hell out of the machine dying, it's not easy to emote about a laptop screen with writing on it.
Reese also had a couple of really badass shootout moments that were beautifully done, I did worry a couple of times him or Root might be going down a blaze of glory.
Samaritan's agenda took an interesting twist and certainly wrapped up 3 strands of the show's branching plots in one swoop, although I thought Control getting blindsided so easily was lame, she should have shot Greer the moment she realized she's been conned.
Keeping viewers is also a key, otherwise you get cancelled, which is the gun that POI is looking down the barrel of. I think they could have done some story changes that would have kept some of the bleakness but also given them a ray of hope entering the final season. As of now, you have to strain real hard to find that hope due to it being blocked by all the darkness they decided to go with.
Also, I think they've become way too focused on the AI war and its tech race while sort of shortchanging much of the human-to-human interaction that made people initially watch this show.
I agree, this is a geek centric board, most of us found our way here through a love of comics and sci fi, but it's not hard to see why some of the general audience can't get into it.
Calling people because they don't like it is the same as the snobby critics that bash movies like Fast 7 and AoU because they clean house at the box office as pure entertainment, while arty "deeply intellectual" stuff limps over the $10M line of they are lucky.
The show has very little humour, is incredibly bleak and has no romance and a hugely far fetched concept set within our real world. you can argue of course that procedurals tend to show the bealk side of life, but usually each week you get a beginning, middle and an end with the bad guy punished. This may seem simple but for many people that is what they want after a hard days work, they don't want to have to worry if they missed a previous ep to be able to understand the one they are watching.