Specifically, it tells us that someone gave the Houthi some (relatively) high-altitude capable systems - the MQ-9 operates between 25,000 and 50,000 feet, well above man portable air defenses like a Stinger or Strela’s capability to detect let alone engage. Being able to engage an MQ-9 at operational altitude means that they had to have stationary or vehicle mounted radar to even detect it and stationary/vehicle mounted missile systems to engage it.
In that case, arm some drones with AGM-88s.