You are misunderstanding the situation. Karpathy claimed that sensor fusion of radar, sonar and vision isn’t working well. He made no such claim about Lidar. Lidar is the sensor that is the crucial difference between Waymo and Tesla's approach to self driving.
The reason he claimed sensor fusion was not working well was due to vendor versioning. He claimed the same sensor from different manufacturing batches performed differently and thus needed to be re-characterized, which then has follow on effects in various math models. Multiply this by many sensors, and the need for replacement parts inventory for a decade or two and the problem becomes intractable was his claim on his most recent appearance on the LF podcast.
