What is the point of Jesus’ parable of the grand evening meal?

Jesus is adding and expanding substance to the wisdom of Solomon Prov 25:6-7. In a sense, Jesus here summarizes the whole plan and purpose of our mortal probation. It is to test (men) to see whether they will seek for worldly things - wealth, learning, honors, power - or whether they will flee from pride, humble themselves before God, and walk before him with an eye single to HIS glory. Humility is the key.