Longbows were pretty ineffective against late period armour like that. And not even plate - mail with gambesons (lots of layers of cloth) was pretty effective at stopping arrows, and full plate harness (2mm thick on average) was for the most part impenetrable even at point blank range.

What longbows were effective at was taking down horses and forcing your enemies to slog a long way on foot with their visors down (restricting vision and breathing). Making the fight a lot easier for your guys.

The end of armour really only came along with gunpowder weapons. Incidentally, gunpowder weapons also made longbows obsolete- largely due to the difference in training needed to shoot a gun (a few weeks on how to load) vs shooting a 100-pound warbow (years to develop muscles).

A combination of longbows and lots of foot soldiers with halberds, which would basically crack the knights like bugs, once they crashed down their horse and couldn't get up anymore.