In this chapter, God makes Ezekiel prophesy against high places where illegal worships are done. In the OT era, the Tabernacles was where legal worships were done because the ark of God was there. However, people set up other places to worship God although He did not allow them to do it. Therefore, the high places became a symbol of illegal worships. To know more about these high places, I’d recommend you read 1 and 2 Samuel, 1 and 2 Kings, and 1 and 2 Chronicles.
Those who set up an idol (while they said they served God of their ancestors) and worshipped at high places are not a small number of people. As we read the OT, we find that the kings and the priests promoted idolatrous worships. The whole nation was worshipping idols.
It is not different today. When the Reformation happened in the 16 th century, the Protestant people emphasized on the lawful worship. Some say that the Reformation is the reformation of worship. Initially, the people of Judah were taught of the lawful worship. King Solomon built the temple of the Lord in Jerusalem and placed the ark of God inside the temple. But soon he and his people started to worship other gods. To be honest, I believe the idolatries never went away because of their corrupt nature. Many in the kingdom of Judah were confident that God would be with them forever because of Jerusalem and the temple. But we will soon read that God abandons Jerusalem because of what He has decided to do with her. As I read the prophetic books of the OT, I get astonished by the similarities that the kingdom of Judah and the Protestant churches (and also the Roman Catholic church and the Northern Israel) share.
While God appointed a certain place for us to worship Him in the OT, it was not His eternal dwelling place. The tabernacle was only a shadow of the real Kingdom. Regarding the only legal and true worship, Christ said in John 4.
The woman said to Him, “Sir, I perceive that You are a prophet. Our fathers worshiped on this mountain, and yet you Jews say that in Jerusalem is the place where one must worship.” Jesus said to her, “Believe Me, woman, that a time is coming when you will worship the Father neither on this mountain nor in Jerusalem. You Samaritans worship what you do not know; we worship what we do know, because salvation is from the Jews. But a time is coming, and even now has arrived, when the true worshipers will worship the Father in spirit and truth; for such people the Father seeks to be His worshipers. God is spirit, and those who worship Him must worship in spirit and truth.” (John 4:19-24)
Here, “spirit” and “truth” are Spirit and Truth (Word, Christ). Most of us can easily get a Bible. It is also free to everyone online. Yet, there is no true understanding of the words of God unless the Spirit gives wisdom. Therefore, God accepts worships from saints only. And that is the Kingdom. However, everyone is welcomed to join a visible church. Joining a church does not mean that everyone can worship God lawfully. Many ignorant Christians including ministers, priests, and theologians promote illegal worships by speaking and preaching lies. However, God protects His saints in each church. As their knowledge of God grows, it becomes difficult for saints to remain in churches that speak lies and promote illegal worships. They are often persecuted and hated by false Christians because they speak truths and are not like them.
But the cowardly, the unbelieving, the vile, the murderers, the sexually immoral, those who practice magic arts, the idolaters and all liars—they will be consigned to the fiery lake of burning sulfur. This is the second death. (Revelation 21:8)
Whoever has ears, let them hear what the Spirit says to the churches. (Read Revelation 2-3)