I don't like saying this, and I really mean no offense and am not trying to be rude, but "get better" is the appropriate response to this. Orc spam is ridiculously easy to counter as all factions.
Lorien: Archers and Beornings.
Isengard: Scouts wreck orcs, dunlanding spam works quite well too.
Rohan: Cavalry.
Gondor: Cavalry, counter free troops from signal fire.
Dwarves: Guardians can each take on multiple hordes of orcs by themselves, excepting Erebor who are really not so great on the field of battle. Iron Hills Guardians with their charge can straight up massacre orc spam.
Free orcs are an essential part of Mordor's balance and playstyle, they are meant to tie up the enemy while your heavy hitters(nazgul, cirith ungol units, summoned evil men) do the real damage.