Reading large numbers of RFID tags has a similar Collision avoidance issue. At the user level, when there are too many tags/read collisions in an area, I reduce transmit power so that my "read bubble" is smaller. You then move the reader around physically until you quit seeing new tags. This is a form of space division.
This is a summary of how RFID solves it at the protocol level, mostly using time division. In practice using cheap readers, I have found this to work up to a few hundreds of tags in one read bubble.
https://www.mdpi.com/2076-3417/8/8/1282