It would depend on how dense the point cloud is, however at 100ft I'm guessing the resolution for something like waymo would be on the order of 10-20cm, which would suggest it wouldn't be able to detect it (at a minimum it wouldn't know its height, and thus it wouldn't know if it's a piece of paper or a steel box). My guess is it also wouldn't know until it's right on top of it

Where did you get 10-20 cm? That sounds wildly off. Commercial lidar would get you to ~3-5 cm at 100 feet easily and Waymo's is said to be better than the commercially available units.

Cameras, like the other lidar-using companies also have, would just like they should here. Teslas problems go beyond a lack of Lidar.