Hi,
You can always play on servers where there are no players, wouldn't that feel like single player?
Anyways as @Spong replied above, devs are working on single player aspect such adding AI, save checkpoints and scenarios.
For routes, devs such as searchlight simulations are developing a US route. Recently, simrail devs were also looking for teams to work on routes from France, Czech Republic, Germany and UK so definitely we will get more routes in future.
As for game feeling arcady, I guess it's each to his own as I find it pretty realistic. Also ETCS is in works, shunting is planned and we already can communicate with dispatch through radio which already makes it much more realistic than any other train sims out in the market.
If you can wait for some more time and give devs a chance, I believe you'll have everything you want from sim as of now and more. As for me Simrail is the best train simulator available right now.