Five times in these two chapters, God makes a direct link between obedience and blessing. Verse after verse describe the Promised Land with all its abundance. But God is not handing the land over to His people without some strings attached.
Clearly He says, all the blessings of Canaan are theirs, IF. Then three times He tells them what will happen if they disobey. First, in 9:14 He warns them they’ll forget Him, then in verses 19, and repeated in 20, He tells them disobedience will lead to destruction.
For myself, I know that when I am blessed by God, it encourages me to obey Him again and again. But I think the Bible is consistent in saying God does not bless disobedience. In fact, there are severe consequences for disobedience.
Sometimes I think people believe God chose Israel (and perhaps the Church) to bless them above all nations, when in reality God chose them (and the Church) to worship Him before all other nations and people, to demonstrate how much He blesses a people who obey Him, in order to draw unbelievers to Himself, so that they can believe, worship, and obey Him, be blessed, and continue to reveal Him to others, and so on, and so on, and so on.
God delights in blessing His children. But obedience comes before blessing, and disobedience comes before a fall.