If what you said is correct, then James would have been in error at Acts 21:18-24.
Being mindful of the context, I do believe it is correct. James was not in error, he understood the bigger picture.
The church was in a state of transition, with unprecedented things happening all around them. Most of the believers were Jewish, and many were still holding on to their Jewish customs and traditions, yet at the same time, they were coming to accept Jesus as the fulfillment of their faith.
In Acts 21, James and the Jerusalem church tried to address the concerns of Jewish believers who were confused by Paul's teachings on circumcision and the Law. By having Paul participate in the Temple rituals and sponsor the purification rites for the men, James intended to show that Paul wasn't rejecting Jewish customs outright, but rather, wanted to include Gentiles in the faith without requiring them to become Jewish converts.
The temple was still standing, the sacrifices were still being offered. Not until later (AD 70) is the Temple system and worship at the temple destroyed. This was the end of the temple system and judgement on those who refused Him The inauguration of true worship empowered by the Spirit occurred at Pentecost.
Concerning the Temple, Jesus said, Not one stone will be left upon another, because you did not recognize the time of God's coming to you. (Luke 19:44).
Concerning worship. Jesus said, Woman, believe me, the hour is coming when you will worship the Father neither on this mountain nor in Jerusalem... (John 4:21)
Salvation is of the Jews....
But the hour is coming, and is now here, when the true worshipers will worship the Father in spirit and truth, for the Father is seeking such people to worship him. God is spirit, and those who worship him must worship in spirit and truth. (John 23-24)
So this event in Acts doesn't necessarily mean that James or the Jerusalem church thought circumcision was still required for salvation. Rather, they were navigating a complex Jewish religious environment, their aim wad to ensure unity and avoid unnecessary controversy. They were already targeted by the religious leader that crucified their King. The time to give their lives for the testimony of Christ would come, but not yet. They were being as Jesus said, wise as serpent's and innocent as doves (Matthew 10:16).
Something Paul himself understood ( Corinthians 9:20-21) ...to the Jews I became like a Jew, to win the Jews. To those under the law I became like one under the law ... to win those under the law.
To those outside the law I became as one outside the law—not being without law toward God but under the law of Christ—that I might win those outside the law.
Paul was clearly willing to adapt and accommodate Jewish customs and practices in certain contexts, yet at the same time maintaining his conviction that salvation came through faith in Jesus Christ, not through the Law or circumcision.