Paul said pretty directly in the Bible there is NOT a distinction between Jew and Gentile.
Yet, there are verses where Paul made distinctions between Jews and Gentile such as Romans 3:1-2 and Romans 9:1-5 that you need to reconcile. The issue that Paul was addressing was that some Jews thought that being circumcised gave them superior status to Gentiles and they were looking down on Gentiles as being inferior, which was creating disunity within the body. So Paul was calling for unity within the body of Christ without respect to our status, not denying that there are any distinctions between Jews and Gentiles.
Paul also told the Colossians,
2:16 Therefore do not let anyone judge you by what you eat or drink, or with regard to a religious festival, a New Moon celebration or a Sabbath day.
If you isolate that verse, then it is ambiguous as to whether Paul was saying not to let anyone judge them for keeping God's holy days or for not keeping them. However, if we look at the context of the views of the people judging them and keep in mind the broader context that we must obey God rather than man, then it becomes clear.
In Colossians 2:16-23, the Colossians were keeping God's holy days in obedience to God's command in accordance with the example that Jesus set for us to follow, they were being judged by pagans teaching human precepts and traditions, self-made religion, asceticism, and severity to the body, and Paul was writing to encourage them not to let any man judge them and keep them from obeying God. So it is ironic that you would try to use this verse to justify your refusal to obey God. In Romans 3:31, Paul said that our faith does not abolish our need to obey God's Law, but rather our faith upholds it, so you should not interpret him as seeking to do the opposite as though he were an enemy of God.
So at the end of the day, the legalists are not in charge.
If God were a legalist for requiring His followers to obey His Law and Jesus was a legalist for living in complete obedience to it and for teaching his followers to obey it by word and by example, then being a legalist would be being in good company, but that is not what legalism refers to. You don't consider someone to be a legalist for thinking that the laws of their country should be obeyed, so legaalm is not about thinking that followers of God should follow Him, but rather it refers to the manner in which someone follows the letter of the law exactly it is written without regard to the spirit of the law or the intent behind it. For example:
Leviticus 19:12 “‘Do not swear falsely by my name and so profane the name of your God. I am the Lord.
Someone who was focused on obeying the spirit of this law would understand that its intent is for us not to swear falsely, whereas someone who was focused on obeying the letter of this law exactly how it was written would understand that we can swear falsely just as long as we don't do so in God's name, which incidentally is the heart of what Jesus was criticizing the Pharisees for doing in Matthew 23:16-22. In Matthew 23:23, Jesus said that they should be tithing without neglecting weightier matters of the Law of justice, mercy, and faithfulness, so this is another form of legalism that undermines the intent of God teaching us how to express His character traits through His Law.
We are continuing to observe Easter on Sunday and that will be that.
The Israelites had daily prayers and offerings, so they worshiped God on every day and it is good to form a tradition of worshiping God on Sunday, but that didn't stop them from also obeying God's command to keep the Sabbath holy, so neither should it stop us. In Mark 7:6-13, Jesus criticized the Pharisees as being hypocrites for setting aside the commands of God in order to establish their own traditions, so the problem is not with someone having a tradition of worshiping God on Sunday, but with them hypocritically setting aside God's command to keep the Sabbath holy in order to establish their own tradition. It is impossible to worship God through disobeying His commands.