In John 4, Jesus' discussion with the Samaritan woman answer this question. The Samaritans were genuine in their worship, but their worship and religious practices were devoid of truth. They worshipped from their heart, their spirit, and were contrite, but they did not worship God as He had revealed himself in scripture. In fact they rejected the temple in Jerusalem in favor of Mount Gerizim.
The Jews in Jerusalem, on the other hand, had abundant access to truth. They had the scriptures, they had the temple system, they had the levitical priests. They followed the religious duties outlined in the Torah well, but their hearts weren’t in it. They had truth, but they lacked a contrite heart. They were very religious, but weren’t true worshippers of the Father.
As Jesus builds His Kingdom, he clearly lays out what He is seeking: those who worship in spirit and in truth; those who worship God from a contrite heart for who he has revealed himself to be in scripture. God hates false religion! He is Holy! His standards are far above the gods of other religions. “God is spirit, and those who worship him must worship in spirit and truth.”
Because God is spirit, I can worship him at all times, because I am always in his presence. His presence is not just at church, and not just when “two or three are gathered”. His presence is here. He is always with me, and he has promised that he will never leave me.
Jesus lost the presence of the Father and the Spirit when he hung on the cross. The Father turned his face away from his Son. As the Storybook Bible says, when Jesus cried out to God, for the only time in history, there was no reply. Jesus was alone, lost, forgotten, forsaken. Praise God that I will never be alone, forgotten, or forsaken. Jesus endured that agony to adopt me into his family, and bring me into his presence forever. He died and rose, then he gave me his Holy Spirit, who is his presence living in me. Before, God’s presence was around me. Now, his presence is in me. He interacts with my thoughts. He shapes my desires. He questions, pokes, prods, until Christ is formed in me. You encourage me, you lead me. Jesus, you said that it was better that you leave and the Spirit come. Holy Spirit, teach me to love you, to trust you, to obey you. You are God.
Because God is spirit, all forms of religious activity without affection for God are worthless. Even worse, they’re an insult to God, as if we could hide our dull hearts from him. No! Those who worship God in spirit and truth are aware that they can’t hide anything from him. On the days when their hearts are dull, they still come to the presence of God, not trying to fake an affection, but they come broken over their dull hearts. They come with a broken and contrite heart.