This may be unlikely but it could be possible that Artyom's flashback was after the war. The trains may not have died immediately and the transition from human civilisation to station cities plauged by mutants and nazis may not have been overnight. I'm sure the developers haven't overlooked a plot point that big. They know what they're doing, we just don't have all the info.
Just to show that there's already an argument against that vision being post-nuclear Moscow, Beebopa. It's certainly a theory though. And I agree. Considering that Dimitri Glukhovsky is also involved in the story (although to what extent I have no idea) I'm sure hoping that they don't have huge plot holes like we're thinking. But yeah. I was confused by this as well. The way he recounted it in the first game, it seemed like he didn't remember anything about it which means he had to have been very recently born. Within 2 years at least. But he seems too old for that in the flashback from the E3 2012 trailer.
It seemed to me that when 4A were making 2033 they said they had Dmitry to help them but they basically went their own way about it and pushed him aside, i'll try and find the video which shows this. I'm not saying he should have designed the game, that would be stupid but I thought it seemed like he was being put to one side.
I don't think he was pushed aside. Nothing in the game suggest that, but that's just my opinion. Obviously, the game is less realistic and more action-packed than the book, in addition to completely omitting many parts of the original plot, but that's what makes it great. It would be impossible to get a 100% accurate recreation of the novel in FPS game format. It would also be quite stupid to transfer all of the story of a book that is over 400 pages long to just one game. I think that 4A Games have shown a perfect example that sometimes less is better. Don't get me wrong - I still think the novel is superior, but the game is the best it could have been with the resources they were given. Anyway, that's just how I personally see it.