It's been a very long time since I played SOMA (played it basically at launch), so I might get some things wrong.
The monsters do add to the story, they were all scientist and researchers going crazy because of WAU, maybe is not much but I personally liked it. The AI was ok I believe, I remember one section where it was very difficult for me to evade the monster, the freaking thing really followed me everywhere and it was pretty tense moment. I finally had to run and the guy almost catches me on an elevator finishing the area. I didn't like the monster designs though, most of them were kind of lame to be honest.
For the ending sequence I understand what you mean, but I think you have to put into Simon's shoes; he went through hell and when he finally saw some hope he grabbed onto it, deep inside he knew it wasn't going to work, but he was to a point of going crazy so I can't really fault him for having false hopes.
Nintendo and PC gamer
