I understand your point of view, I really do, but you need to understand that if we were to supervise and manage all the user made mods we wouldn't be able to do anything else. There are tens of thousands of mods in the workshop and for us to check they all work, well, it just isn't feasible. This is also why mods are optional, we never force anyone to use them.
Now, had we made it mandatory to use mod X Y and Z then of course we would have a responsibility to make sure they worked, however this isn't the case and therefore we are not going to take responsibility for mods and their compatibility. We simply don't have the manpower nor time.
I've had these discussions before, I worked for Blizzard and Wargaming in the past, and with updates and expansions popular mods tended to break and cause the customers frustration. But I think our community needs to understand that mods are not made by Paradox or Colossal Staff, they are made by the community and the author is solely responsible for updating them.