I think the idea and concept is good but without spoiling the movie too much, here's my take ( I am writing this fresh after watching )
By the middle it was VERY predictable what might happen. They tried to build on the main characters and for us to feel for them, but I hardly felt any emotions, the buildup simply wasn't strong enough.
On the issue of selfishness + selflessness, other survival based movies have touched on this Heaps better. District 9, Train to Busan etc. just to name a few off my head.
I like the idea of a dangerous fog over Paris, the trailer was very captivating, as was the first half of the movie, then it goes wayside very quickly.
in all I would say it was a wasted opportunity. There was a great missed potential here. It centers only on so few characters yet I do not feel much for them, and at the end of the movie, you are left with no answers to the greater whole .. good Concept, but too shallow
5.5/10 at best for me.