It's an extra sensor you'd add into the mix, you'd still have cameras. Like the radar sensors. I think the reason Teslas don't have it, is because the sensor hardware was expensive a few years back. I assume they are much cheaper now.

Tesla have also backed themselves into a corner by declaring that older models are hardware capable of FSD, so they can't easily add LIDAR to new models without being liable for upgrading/refunding previously sold models.