Humanistic Judaism doesn’t proclaim that there is no God, but it does do without God. It sees no evidence for the existence of a supernatural being. Most Humanistic Jews regard the question of God’s existence as either meaningless, or irrelevant.
It finds no meaning in the worship of God, whether or not God exists. So Humanistic Jews do not pray or refer to God or the supernatural, or use worshipful or prayer-like language.
It gives no moral authority to God.
I respect the right to believe what you want, but… isn’t that going against basically everything Judaism stands for? It says that they stand for Jewish culture, but Israel’s entire culture was based on the Mosaic law.