-——they lack effective armor, airpower, and mobile artillery——
——and use lots of artillery and air-strikes to root them out and kill them.-—
the two statements appear contradictory
The IRGC does not possess sufficent organic armor or artillery for proper combined arms attacks (they leave that to the regular Iranian military, who are not used much outside Iran).
But when they are defending, they can dig in, pepper urban terrain with IEDs, and use that terrain to their advantage, requiring the attacker (us) to pry them out and use our own air and artillery to dig them out.