You're mixing some things up. Paul knew that the Levitical priesthood was no longer in effect (see Hebrews) so all of the functions of that priesthood outlined in scripture couldn't be performed. Paul knew that the sacrifice of Christ was sufficient so no more animal sacrifices had to be performed. Paul recognized that, as you said, the Jews had instituted many customs and traditions that were non-biblical. Jesus railed against these non-biblical customs. In many cases these ideas and customs had been incorporated from pagan religions and thought.
Jesus and his followers were basically trying to get back to the religion once delivered, worship of the Lord without all the Jewish and pagan influence. They didn't intend to completely create a new religion. They didn't intend for Christianity to jettison everything the Lord had already delivered. They knew that that certain things were changed under the new covenant. I'll keep saying this till I'm blue in the face, but these things are listed in Hebrews and they're very specific. Sacrifices and the Levitical priesthood are the primary changes brought about by the new covenant. However, the first Christians kept and preserved things such as the holy days and the food laws. Historically you can trace when traditional Christianity officially outlawed sabbath keeping and other so-called "Jewish" customs. Mostly it had to do with anti-semitism and from a desire not to resemble Jews.
May we bless YHvH for sending His Lamb to be sacrificedshalom b'SHEM Yah'shua HaMashiach
as a blood covering for all of our sins forever.We are blessed that Yah'shua rose on the Feast of First Fruits
as an example of offering to YHvH the first and best of the
harvest of salvation for all who will call on His NAME.
Once again you deny the truth of scripture. For starters they were not brought under the dietary laws -
Acts 15:28 For it seemed good to the Holy Ghost, and to us, to lay upon you no greater burden than these necessary things; 29 That ye abstain from meats offered to idols, and from blood, and from things strangled, and from fornication: from which if ye keep yourselves, ye shall do well. Fare ye well.
As far as keeping Jewish holy days - Show me where outside of the Gospels where it shows that gentile believers in Christ were required to keep the holy days? I've already shown you where they were specifically freed from those things by Paul. Go ahead, be blue in the face - you are setting yourself against scripture.
However, the first Christians kept and preserved things such as the holy days and the food laws. Historically you can trace when traditional Christianity officially outlawed sabbath keeping and other so-called "Jewish" customs. Mostly it had to do with anti-semitism and from a desire not to resemble Jews.
I'm sure you could - but the fundamentals were already in place, with believers already meeting on the first day of the week in recognition that it was the day of His resurrection.