To be fair, no flight sim gets much more than 60fps at best, let alone one just released. 30fps is perfectly playable for a simulator. I get the impression that a lot of people complaining about this game have never played one before.
It feels like a slideshow in cities, it's not even a stable 30fps, I started in London and it was 20fps. I wasn't even using the highest settings.
The visuals are good in places but performance is horrible, I guess you could just stay out of cities where it's 90fps+ but that's not much fun.