its kind of true
shield walls done right can make archers useless but the AI doesnt use them vs mostly archers army
the cav are good vs ranged units with 100 cav vs 300 rangers and the cav having the strategic location to jump the cav choices instead to attack infantry and gets deleted
mounted archers deciding to flank instead of circling making them open for a counter attack
ranged units targeting too close to friendly units or shields instead of enemy archers or un-shielded units also can make them useless