I don't think that is necessary right now.
Since you said you have taken a lot of subscriptions out, I suspect you crossed the invisible barrier and are now stuck in a dark place.
First, run NameMyRoute.exe from the Railworks folder.
It will show a list of all your routes and scenarios.
You'll find that Route Properties cannot be read, that is because the route is still packed in an .ap file. Unless you downloaded a Workshop route, you can ignore these unreadable routes. The UUID shown is the name of the folder under Content/Routes.
When you scroll through the list of scenarios, you'll probably find corrupted ScenarioProperties.xml messages.
I don't trust these corrupted scenarios so I deleted them all.
On next start and Workshop synchronisation, Steam downloaded and installed them again, many and even others still corrupted. On a next start of Railworks, it dumped out on me while "saving the scenario database". And again, and again ....
So I took a drastic measure, and renamed the Routes folder into Routes_broken and created a new, empty Routes folder.
This way, when you now synchronize against your Workshop subscriptions, Railworks will only download all your subscriptions, a slow process.
It should now save the scenario database, hopefully. There should be less scenarios shown by NameMyRoute.exe, as all the default and DLC ones are in the Routes_broken folder.
But now you are stuck with only a few Workshop routes you can run, all other routes are incomplete and will crash.
So I copied my install to a non-Workshop Railworks folder, where only default and DLC scenarios remained in the Content/Routes folder by deleting most of the Workshop stuff I could find. Not very useful, as many Workshop scenarios, like Elphaba's are quite good.
In the other, still broken install, I cannot play at all, the game never saves the scenario database. So I ditched all the non-US routes, and finally the game would start. Synchronizing is no good, as the database would grow and crash the game again, unless you unsubscribe from all of the non-US items.
I really don't know how to proceed, and repair my broken install. DTG needs to sort out the number of subscriptions bug or impose a limit on the number of subscriptions a player can take. Sorry that I couldn't help you.
I think the suggestion of unsubcribing from many Workshop items is a valid one. But if the actual item isn't deleted from your broken install as mentioned, it will not help.
Perhaps then, you can create a working, cleaner install by first uninstalling most or all of your routes (and perhaps DLC that come with scenarios) throught the Game Properties tab in Steam, then re-name the Routes folder, create a new empty Routes folder, re-install the uninstalled routes (and DLC) by ticking the boxes again, make a backup of the fresh Routes folder, and have Railworks synchronize against the significantly reduced number of Workshop subscriptions, and hope for the best.
Less (subscriptions) is more.