You don't know how games work.
Just because some MMO games exist does not mean ALL games can be MMOs. This game uses an in-house engine (the base software upon which the game was built), and it does not support an MMO.
The mod you have is called TruckersMP. It uses a bypass to the engine's limitations to allow other players to interact with each other. However, in doing so, many aspects of the game had to removed (such as AI traffic) and others are bugged (such as desynched weather). This is simply because the game as it is can not handle a multiplayer session, much less be purely hosted as an MMO. Now, think to yourself for a moment... if the developers of the TruckersMP mod put in all the effort to making that mod (which is not easy, hence why they are the ONLY multiplayer for the game right now), why won't they patch it to fix the weather or add AI traffic?
Answer: it's simply not possible on the game's current system.
This would take rewriting the entire game engine to support multiplayer. Yes, SCS has eventually plans to possibly do something like this, but do to the work required to rewrite it, how much the community here doesn't care about such a feature, and the general cost of maintaining servers, it's on the back burner until further notice. They also have no plans of it becoming an MMO, as they would lose almost all of their business for that.
I read these suggestions as I am very open to change (and suggest my own changes all the time). However, I also share my views against suggestions to ideas such as this which would A: ruin the entire idea of the current game, and B: require an entire rewrite outside of the game's scope.
If you can't handle people disagreeing with you, you probably need to leave the internet, as anywhere you post you will have people disagreeing with you.
You are not off to a good start here. Your very first post being a suggestion to rebuild the entire game, followed by nothing but arguing and calling people terrorist...
I wonder why the moderators even bothered approving your posts...?