When a person has a confirmation bias toward a certain doctrine, which in your case is the "idea" that angels can fall and sin, its like God has painted the most beautiful artwork and in one smudging action, its lost on you forever.
Do you have a confirmation bias against it?
What does the rest of scripture say about the existence of satan the devil and those of his angelic ‘cohorts’ who followed him into rebellion? They have a place prepared by God from their beginning to bring them to justice....and Jesus will make sure that all rebels will join satan and his demons in this place of eternal annihilation.
Concerning the "sheep and the goats" Jesus will say...
“...to those on his left: ‘Go away from me, you who have been cursed, into the everlasting fire prepared for the Devil and his angels . . . .These will depart into everlasting cutting-off, but the righteous ones into everlasting life.” (Matthew 25:41, 46)
Are these creatures mythological? Jesus doesn’t think so.....
When a legion of demons had possessed a man, they begged Jesus to send them into a herd of swine and when he did, they drove the entire herd off a cliff. (Mark 5:1-13)
Are these mythical creatures? How do 2,000 pigs get to jump off a cliff into the sea and drown of their own volition?
Can free willed spirit beings fall? Yes they can...and they did, just like the free willed humans did. Revelation20:1-3 tells us that there is an “abyss” in which the devil and his demons will be imprisoned in order for the Kingdom of God to undo all the damage that the rebellion in Eden caused to all of us. A thousand years of God's Kingdom rule will see what Jesus said in prayer, come to pass.....God's will can then be "done on earth as it is in heaven".
Do you understand the implications of God giving his intelligent creatures free will?
It was intended as a gift, but abuse turned it into a curse.
All was well in heaven until God decided to bring about material creation. No angel had rebelled until then because there were no inferior creatures in existence. If the original angel who made himself “satan the devil” was discontented with his lot, he had no real way to express it. If he desired the worship that belonged to his God, then how could his fellow angels worship him if they were his equals? He could be their leader, but not their god.
With the creation of humankind, the situation changed completely. As a powerful spirit creature, satan could get worship from these lesser beings and become a “god” to them.... but first he had to separate them from their Creator. He was right there in the garden as a guardian (a covering cherub) and plotted his course to gain what he desired. When he told the woman that she would be “like God”, he was really expressing his own desire to be “like God” and have the humans worship him by doing his bidding.
This is the Bible’s narrative from the beginning. Without satan there would have been no rebellion among the humans, and no need for God to send his Christ to rescue them.
We see from the account of Job, what satan is capable of doing to a human being, and why he would choose to make them suffer.
Job actually represented the entire human race because....
"The Lord said to Satan, “Have you considered My servant Job? For there is no one like him on the earth, a blameless and upright man fearing God and turning away from evil. And he still holds firm to his integrity, although you incited Me against him to ruin him without cause.” 4 Satan answered the Lord and said, “Skin for skin! Yes, all that a man has, he will give for his life. 5 However, reach out with Your hand now, and touch his bone and his flesh; he will curse You to Your face!” 6 So the Lord said to Satan, “Behold, he is in your power, only spare his life.”
What do you see there? Satan said "all that
a man has, he will give for his life"....he didn't say "everything Job has"....so Job was representing the whole of humanity, showing that no matter what the devil does to us, we will not blame God, abandon him, or curse him. Throughout his trials Job left himself in God's hands, remaining faithful without knowing why he was being targeted. We do know.