No, it is not true. God never changes: He is the same today as He was 3,000 years ago - and He will be the same 3,000 years from now as He is today. As the Bible says, "I the Lord do not change" (Malachi 3:6).
The world does change, however, and it's true that God's people in Old Testament times faced different challenges from those their descendants would face. Often they were surrounded by hostile nations that were determined to stamp them out, and God said they must defend themselves against their enemies in order to survive. But repeatedly God assured them of His love; the prophet Jeremiah wrote, "The Lord appeared to us in the past, saying: 'I have loved you with an everlasting love; I have drawn you with loving-kindness'" (Jeremiah 31:3).
We see God's love most clearly, however, in the person of Jesus Christ. He was God in human flesh, who came down from heaven to express God's unchanging love to us. He did this by taking upon Himself the judgment we deserve for our sins, dying on the cross for us. The Bible says, "This is love: not that we loved God, but that he loved us and sent his Son as an atoning sacrifice for our sins" (1 John 4:10).
Have you opened your heart and life to Christ? The greatest discovery you will ever make is that God loves you, and He wants you to be His child forever. Give yourself to Christ today.