My interest in driving trains in sims has declined in the last year or so. I haven't played MSTS for months, but it still works on Windows teN.
At the end of the day, there aren't huge numbers of folks playing GTA Vice City, or even Stunts. The reason is because they use old technology, just like MSTS does. The dwindling activity levels in this section of RP are a clear indication of this.
Don't expect it to suddenly increase. It is a 2001 game, with no core improvements, unless you count Open Rails compatibility.
There is certainly no longer a need for multiple subforums for this game or any of the other sims mentioned. Many of these threads can be archived, with one section for train simulation retained.
Having so many subforums is like running a regular bus service using an artic through a country town that has a population of 25.