there's inherent problems too.

• Except for where they screw into the socket, incandescent bulbs are point sources that emit light in all directions. About half of it comes out "backwards" and then is reflected out with a parabolic reflector. So oncoming traffic sees a large but relatively low-intensity light source. Power LEDs are bound to a flat substrate and the light comes basically straight out. This means that manufacturers are able to dispense with the reflectors. When you're behind a car with LED taillights, you see a bunch of little bright points instead of a big soft one. Total lumens might be the same, but the small high-intensity points are more likely to dazzle you.
• LEDs are much bluer than incandescents; making them warmer comes with its own downsides. Idk if this really matters though