I love how the message translation of the Bible puts this verse, 1 Samuel 15:22-23 Then Samuel said, Do you think all God wants are sacrifices— empty rituals just for show? He wants you to listen to him!
Plain listening is the thing, not staging a lavish religious production. Not doing what God tells you is far worse than fooling around
in the occult. Getting self-important around God is far worse than making deals with your dead ancestors. Because you said No to God's command, he says No to your kingship.

The truth is that there is nothing wrong with doing something which is beautiful and lavish for God, the woman who broke her very expensive perfume jar over the feet of Jesus in the days leading up to the cross, did something beautiful and lavish and extravagant for Jesus, in a beautiful act of worship. But here Saul is clearly making it about him. He says its about God, he says he kept back the best for God, but it is about his appearance, how he looks, what people think of him. That is religious! That is religion, and its empty, and it has no real worth, because obedience to God is what counts, to what God has asked for, not what He has not asked for