I don’t think that Jesus at all repudiated the idea that suffering, at least possibly some suffering, cannot be the result of sin; or that God no longer visits the iniquity of one generation unto the next. I would also disagree with the author.
To give a few examples:
Jesus, being God, knew all things. He healed many people, but there was one person, as recorded in John chapter 5, whose illness seemed to be the direct result of his sin. After Jesus healed this man he told him, “See, you are well again. Stop sinning or something worse may happen to you.”
Then, as seen in I Corinthians chapter 11, Paul speaks about those who were eating the Lord’s Supper in an unworthy manner. He warned them, “Each one must examine himself before he eats of the bread and drinks of the cup. For anyone who eats and drinks without recognizing the body eats and drinks judgment on himself. That is why many among you are weak and sick, and a number of you have died.”
As far as God visiting the iniquity of one generation upon the next, the Old Testament says in Deuteronomy 24:16, “Fathers shall not be put to death because of their children, nor shall children be put to death because of their fathers. Each one shall be put to death for his own sin.” So each person is guilty or acclaimed innocent by their own actions.
But there were some cases where the sins of one generation were felt by the next generation. Usually, a generation in the Bible is roughly thirty years long. The Bible says that both Jewish exiles–one into Babylon and the other into Assyria–were the direct result of sin. The Babylonian exile lasted for about 70 years–2 or so generations–so one generation sinned, and the next was still suffering the consequences. The Assyrian captivity lasted for about 200 years. So subsequent generations were affected.
A more current example would be the destruction of the Temple in 70 a.d. Jesus prophesied that this would happen. (Luke 19:43-44) He said it would happen as a direct result of sin–the Jewish Nation as a whole did not accept their Messiah. So the Jewish people were once again exiled. In this case the result of this sin was felt by how many generations? I’m not a mathematician, but around 60 generations? From 70 a.d. to 1948.
So God has not changed and Jesus didn’t change doctrine from the Old to the New Testament.
When Jesus said that God allows the rain to fall on the good and the evil alike, he was saying that God has blessed all people with his abundance. God has given us rain to make our crops grow, and he has supplied us with food. God’s bounty is enjoyed by all–the good and the evil alike. This verse that you quoted in your initial post isn’t speaking of the results of sin.