This is a popular refrain among people who are not studying Tesla’s progress particularly closely, and/or are unfamiliar with the utility LIDAR actually provides. Tesla FSD still has some way to go before it is ready to be a properly autonomous robotaxi — but where it's failing are not areas where adding LIDAR would help.
Tesla's vision stack is already sufficiently capable of mapping the three-dimensional environment with sufficient precision.
Tesla FSD needs better planning strategies when faced with unusual obstructions like novel construction zone diversions. Adding LIDAR wouldn't help there. Tesla FSD desperately needs more road sign reading skills. LIDAR can't read road signs. Tesla FSD will eventually need to recognise law enforcement officers and respond to hand gestures. LIDAR cannot translate hand gestures into actionable driving instructions, and certainly can't assess the plausibility that the person is a LEO.