One of the add-ons has likely overwritten a default texture or effect file. Unfortunately, simply removing the add-ons might not be enough to fix it.
Try restoring (system restore) to a point in time when you knew the sim was working properly.
Flight Simulator and other chat
https://forums.simviation.com/phpBB3/
https://forums.simviation.com/phpBB3/viewtopic.php?f=21&t=176333
OldAirmail wrote:Another choice would be to re-run the installer again. It'll replace any textures that you've added. Then just reinstall you add-ons one at a time until you find the problem software.
The more experience you have, the less likely you are to do that again. We've made the same mistakes at one time or another.