>They could have easily set this movie anywhere else and it would have worked the same,they didn't even make use of the setting.

Setting it on a moving train automatically limits the options of escape as well as who can get on. That can only happen at stops, and even the stops were added into the plot line with Ladybug being unable to escape, trying to trick the assassins at the various stops, etc.

The train's specific setting was used when they incorporated the dining car fight and the various props that would be found there. Also when they were in the Quiet Car and had to keep their conversation and fighting to a minimum. Having been in Quiet Cars, there are absolutely passengers who will call you out if you make too much noise.

It's been a couple months since I've seen it so I can't recall any more examples right now.