You can fix the grainy shadows and textures yourself. At least revert them to the way they were at launch, where you’ll only occasionally get a small amount of grain along the edges of dark clouds under certain lighting conditions vs this grainy mess we’re seeing everywhere now. At launch, the small grainy edges in clouds was acceptable to me. Or at least a giant improvement over what’s there now.
The grain issue is a combination of film grain effect, and then excessive sharpening applied over top of it. Those settings are not exposed to us in the in-game menus, but can be disabled from the config file.
Open the file below in Notepad (back it up first just in case)
<yourWindowsProfileFolder>\AppData\Roaming\Microsoft Flight Simulator\UserCfg.opt
Set both Film Grain and Sharpening values to 0, and then boot the game. Grain will be gone.
The end result is an overall image that’s a touch less sharp, but you can bump up render scale about 10-20 and it regains its sharpness. The performance tradeoff for increased render scale vs turning off those other 2 effects is about the same. Not really noticeable to me at least at 3440 x 1440. If you’re running at 4K with 100 scale rendering, that might cause a performance hit.