You might be thinking of radar, which Tesla is also no longer putting in their cars.
IR lidar would be pretty useful in rain and fog, I'd think. But I'd rather have all three -- lidar, radar, and visual. Hell, throw in ultrasonic sonar too. That's what Kalman filters are for. Maybe then the system will notice that it's about to ram a fire truck.
Some potential improvements are relatively trivial, even without getting into the hardcore linear algebra. If the camera doesn't see an obstacle but both radar and lidar do, that's an opportunity to fail relatively safely (potential false braking) rather than failing in a way that causes horrific crashes.
Bottom line: if you can't do sensor fusion, you literally have no business working on leading-edge AI/ML applications.