Ground units cannot even attack it. Even Scorpions and TOW Launchers, which supposed to be hard counter to venhicles with their amazing range, cannot shoot down helicopter. So what is the solution?
How to Counterplay Against MI-23
Most of support also target only ground units (didn’t check A-10 bombing), so they cannot help.
So the only way to beat MI-23 is to use another helicopter.
Or to use the defense command with your anti-air scorpions/tow missiles to make their range long enough to reach the helicopter.
You’ll also probably need some sacrificial victims in front of them to give them enough time to aim and fire before being instantly vaporized.