Before his conversion Paul had regarded himself as blameless "touching the righteousness which is in the law." Philippians 3:6. But since his change of heart he had gained a clear conception of the mission of the Saviour as the Redeemer of the entire race, Gentile as well as Jew, and had learned the difference between a living faith and a dead formalism. In the light of the gospel the ancient rites and ceremonies committed to Israel had gained a new and deeper significance. That which they shadowed forth had come to pass, and those who were living under the gospel dispensation had been freed from their observance. God's unchangeable law of Ten Commandments, however, Paul still kept in spirit as well as in letter. {AA 190.1}
What could "divinely appointed services" mean other than the feast days? What other could "the ancient rites and ceremonies committed to Israel" include?
In the Galatian churches, open, unmasked error was supplanting the gospel message. Christ, the true foundation of the faith, was virtually renounced for the obsolete ceremonies of Judaism. The apostle saw that if the believers in Galatia were saved from the dangerous influences which threatened them, the most decisive measures must be taken, the sharpest warnings given. {AA 385.2}
Excellent quotes!
The temple rituals and ceremonies were to lead people to Christ and teach them about the work of Salvation Christ would do for a lost world.
However, like many people today, the main Jewish population thought it was something they could do to merit their own salvation. The focus turned away from the ONE who offered salvation and centered upon self and what they could do to earn salvation.
Those who fall into that trap, like Paul prior to accepting the gospel, tend to regard themselves as good "touching the righteousness which is in the law", as they boast that they are pretty strict in checking off their list of does and don'ts, while those who were weaker really had not hope.
However, when we come to Christ and accept His righteousness then we no longer "boast" about our strength, for we realize that's all "dead works".
Real faith and salvation and true overcoming, is all from Christ!
Galatians 6:14 But God forbid that I should boast, save in the cross of our Lord Jesus Christ, by whom the world is crucified unto me, and I unto the world.