Towards the end of Avengers: Endgame, we see Thor, Captain America and Iron Man fight Thanos, who has a particular bladed weapon.
At the start of this fight, we see Iron Man form some sort of blade with his suit, which he then uses to deflect several blows from Thanos' blade. But then later we see Thanos partially destroy Captain America's shield. This item is meant to be extremely durable, being made of Vibranium, a metal which is established as the strongest substance we have access to on earth.
My quarrel is not with this, but the fact that, as mentioned earlier, at the beginning of the fight Iron Man's suit manages to take several hits with minimal/no damage from the blade.
Even if Iron Man's suit is made of Vibranium, it is later established that the weapon in question is capable of tearing through Vibranium.
How can Iron Man take blows from Thanos with no problem, but Captain America's shield cannot?