I asked you to read the sermon on the mount to see how long it would take. I did the same and it took me 20 minutes. That is not a long time in comparison to most sermons. We do not all read at the same pace. Some are speed readers and those reading times would be shorter.
During my reading I noticed two things. I did not pause in my reading to allow those words to sink in. Pastors do not rush through a sermon and often pause, gesture, and move from side to side looking his congregation in the eye.
The second thing I noticed was that the Holy Spirit would remind me of other scriptures that I have read over decades and connected what Jesus was saying with other passages in both the Old Testament and the New Testament. Those listening to Him on that mount did not have all that information nor had the Holy Spirit been given them.
Sermons are not given these days as Jesus gave the sermon on the mount. All that Jesus spoke that day deserves more than just a quick read. They deserve discussion so that their importance is not easily discarded. Jesus said before that sermon, Matthew 4:4 But he answered, “It is written, “‘Man shall not live by bread alone, but by every word that comes from the mouth of God.’”
Bread has to be digested in order to nourish the body, as does His Word.