There was a lot to really like in the movie
*An effort at some cinematography, the opening shots, to the SF bridge shot in the morning, it was refreshing for a Blumhouse horror movie
*The solid acting across the cast, esp. the maniacal tech bro, he was excellent in a small role
*The architecture and setting, reminded me "Jagged Edge" and "Play Misty For Me" at times, in terms of themes and locales
*the score
*The gaslighting/toxic relationship elements felt earned, relevant, and never ham fisted
If I wanted to complain a little, some scenes dragged, and the trope of the movie monster dismantling an isolated police station of some kind was tiresome, and some of the "crazy woman" who no one believes felt very grating and raked over at times, but that may be unfair. The attic scenes also, felt a bit absurd. Don't go in the attic.
Yes, the conclusion, when there are verified men running around in invisible suits, I wouldn't act so confident of getting away with that, and the pre reveal reveal was pretty weak too. If they took everything and added like an extra layer of seriousness and effort, plus 15 million, you could have something close to "Ex Machina", a movie with a somewhat unbelievable premise, that is as serious and good as they come, as it is, it is a great horror movie, not quite in the league of The Witch, or It Follow's but not far behind. The critiques I read that Whannel's script and direction is light, but stylish is dead on.