I can only imagine that there are some specific areas of the sim that are integral to the base sim. Having 3rd party software mucking about in the core sim is just a really bad idea.
The sim is ported to accept specific classes of modifications. There is very little that is off limits to third part development. A significant investment in partnership agreements with both weather and traffic providers also creates some hurdles.
MS/Asobo have been very upfront about the future potential for outside developers to create add-ons for the sim. Just as it has been with previous versions, there will be copious amounts of stuff to spend your money on, eventually. This sim is creating new challenges for those 3rd parties with new languages and API’s. You stated you know nothing of coding. I suggest do some reading and you will find that creating new, quality content for the sim is not a weekend project.
Patience is going to be required. We are years away from the warehouse full of add-ons worth buying.