I think it is whatever you want it to be! You can drive trains with realistic signalling and safety systems and duties to do like stopping at stations or shunting - so in that way it is a simulator as you are simulating the experience of driving a train. You can travel as a passenger or stand on a station watching trains so it is simulating being a passenger or a train spotter or railfan if you like. You can, if you want, going round collecting items and gaining points so in that way it is more of a game. So it is both.
I would like to see some of you stop for 2 hours in the intermediate station driving a EuroNight service, as happens in reality to offer a few more hours of rest to passengers in the berth. Obviously without skipping the time. So, if your service crashes, the next day you sell your game and PC and go jogging to forget. The first time may be thrilling, but the second and third? 30-40 minutes just to start the train and enter service. The first few times it's cool, but then what? I think it is obvious, when it comes to videogames to assume that with the term "simulator" it is assumed that it is a simulation-oriented. Arcade? You probably haven't seen video games born in the 70-80s, when Out Run and Hang-On were popular in the arcades/bars
I made a scenario for TS1 on the Riviera in the 50's route following a working timetable on a busy summer Saturday which included a wait of 15 minutes or so at Torquay. I uploaded it and that got a couple of complaints that people didn't like waiting with nothing to do for 15 minutes. I said to go and put the kettle on or something or do some vacuuming!
When I read some of the comments on this forum calling for maximum authenticity, I always hope for somebody to request a "perma-delete profile" feature if they attempt to drive a journey/scenario without safety systems, or they pass a signal at danger or speeding for more than 5 times. Something that would result in loosing your job or license. For me this should be part of the simulation experience for drivers. I myself enjoy the lightweight nature of TSWx. But for me the hardcore gameplay should carry some weight. I would also like to have realistic waiting times when you need to do some paperwork, or route review. Something like an in-game document showing you details of the route ahead with arrival/departure times. Or if they wish to move towards a game experience they could utilise the marker system to learn tidbits about the history of the stations, tracks, historical buildings. Much better to explore for these than putting the same poster up. I may drop this to the suggestion section.