Angels can be present in vast numbers and yet remain unseen

2 Kings 6:15-17
When the servant of the man of God got up and went out early the next morning, an army with horses and chariots had surrounded the city. "Oh no, my lord! What shall we do?" the servant asked. "Don't be afraid," the prophet answered. "Those who are with us are more than those who are with them." And Elisha prayed, "Open his eyes, LORD, so that he may see." Then the LORD opened the servant's eyes, and he looked and saw the hills full of horses and chariots of fire all around Elisha.

The horses adn chariots of fire mentioned here are learly heavenly creautres. Elish couls see them but his servant could not until his eyes were open. Fire speaks of the presence of God adn the the horses and chariots are the appropriate counterpart to a hostile Aramean army. No doubt the norm is for us not to see the angels. There is no obvious need for our eyes to be opened to the presence as Scripture confirms the fact again and again.