I was looking at the Tadami screenshots which look very clean. I also read some consensus that most routes are very clean. When I was thinking on how much dirt and litter should be applied I was thinking the litter in stations changes during the day. All the passenger traffic generates a lot litter and then someone comes to clean it up. Couldn't there be made a litter sequence that changes the look of the stations over an entire day?
If think this is a huge immersion topic in general. There has to be a lot more litter on stations, but also everywhere else! Maybe let some papers fly through the air sometimes, have some old cups or books lying in the track bed
The tracks, platforms and trains where I work are never sparkling clean (except for the platform/s which are currently being refurbished). More "weathering", so to put it, would put us closer to real life, its a simulation after all.
I mean't the litter on the platforms. Weathering overall should be improved (also on trains) but that's not something dynamic. Or at least I don't expect to be driving the same route in 10 years. Probably will have bought an update by then