Engineer air launchers are useless

Air defense launchers seem useless. Can easily spend a whole game trying to take out aircraft and not even get a kill, barely a hit or two.  It only works on noobs. 

1. Generally players know how to fly, expecting some noob to blow flares early isn't a valid response for how these perform. The game has been out a while now and noob pilots are more of an exception. 
2. Choppers and aircraft easily fly low to avoid lock on or break lock on progress
3. Even if you get a shot off, they just flare and bail out of range for a moment. It's barely even a threat.  
4. If you do get a shot off usually it misses or collides with some environmental bs
5. Even being able to reload a launcher faster than a flare isn't useful, the aircraft is usually gone by then or just flys low. If you do manage to reload for a second shot, go back to point 2 and 3. 
6. If feels so redundant holding an "air defense" weapon when there is a chopper literally circling around above you, and you can't even shoot the airborne enemy with your "air defense" weapon because it's not even possible to lock on. Your more likely to kill the pilot with machine gun or snipe than bother attempting to use these launchers.  

Normally I'd use any other launcher and have a good time, but trying to do any achievement specifically involving kills with these launchers feels insufferable and boring.