I was reading one major issue with lidar is bad weather. Microwave can apparently do that OK but the wavelength is a trade off between accuracy, object size and weather/interference avoidance.
In fairness, bad weather is a big challenge for human drivers as well. Largely because we don't realize how much more difficult it is to drive with limited visibility/traction and don't slow down enough.
LIDAR is the only way to go, imo.