The SNR for flash Lidar is really low because you spread the beam out over such a large area.

Most automotive Lidar already operate in a “photon starved regime”, ~200-300 photons per return[0]. If you spread that over the entire scene, your snr drops quickly.

This forces you into 1550nm, and a large detector array and high power laser at 1550nm is extremely expensive.

As for MEMS, it’s been a while but I think FOV/steering angle range , steering speed and even maximum beam power were concerns

EDIT: my Lidar friend Jake reminded me that the appetizer size is also an issue with MEMS- smaller aperture = less light collected = lower SNR

[0] https://www.hamamatsu.com/content/dam/hamamatsu-photonics/si...