Sunday worship / Christmas / Easter and all the rest....

Nah .. I grew up Southern Baptist and we always worshiped on sunday.
Seems a little self-righteous to judge people just for what day they worship
Also Christians are not subject to Mosaic law, as per the covenant of the New testament so yeah, it's pedantic

The New Testament obviously does not observe the Sabbath, Paul told us "on whatever day". However, as a type it is very important, just read Hebrews and just because it isn't part of our covenant doesn't mean it isn't important, it is part of the Old Covenant.

In Colossians Paul tells us that the Sabbath days and holy convocations are prophetic, a shadow of things to come. Many pastors refer to Israel as "God's prophetic time clock" so if you are trying to tell time it makes a great difference. Also if you are navigating across the ocean it is crucial to have a good clock, you can't tell where you are unless you have a very accurate clock.

The New Testament obviously does not observe the Sabbath, Paul told us "on whatever day". However, as a type it is very important,
just read Hebrews and just because it isn't part of our covenant doesn't mean it isn't important, it is part of the Old Covenant.

Keeping the Sabbath is basically impossible. That's why the apostle Paul said Christians don't benefit from keeping the old Jewish laws.
Imagine going to church and your pastor asks help move some chairs and you say sorry bro can't do it that would be working on the sabbath.
If you really want to be technical about it, just the act of getting out of bed and putting on clothes is doing work on the Sabbath

The Old Covenant is passing away and becoming obsolete (see Hebrews 8:13).

The New Testament obviously does not observe the Sabbath, Paul told us "on whatever day". However, as a type it is very important, just read Hebrews and just because it isn't part of our covenant doesn't mean it isn't important, it is part of the Old Covenant.

In Colossians Paul tells us that the Sabbath days and holy convocations are prophetic, a shadow of things to come. Many pastors refer to Israel as "God's prophetic time clock" so if you are trying to tell time it makes a great difference. Also if you are navigating across the ocean it is crucial to have a good clock, you can't tell where you are unless you have a very accurate clock.

Okay so we're in agreement at the apostle Paul says Christians don't benefit from following the Mosaic law so why the hostility?

What part of the old covenant is superior to the new covenant?

Zero.......

There was no hostility. Man lives by every word of God. To discount major portions of the Bible is not wise. Yes, we are told in the New Testament that we do not need to keep the Sabbath however we are also told that if we want to understand God's prophetic time clock we have to know His festivals and His Sabbaths. If you did know that then you would also know that Saturday is not the Sabbath. Each month begins with the new moon. The seventh day is just that the seventh day starting your count from the new moon when you first see the crescent. A full moon will also be a Sabbath, seven days after that around the waning half moon will be the third Sabbath and then the New moon will be a 2-3 day "new moon Sabbath".

The idea that some people will become legalistic and self righteous about "keeping the sabbath" and then they don't even keep the sabbath, they keep "Satan's day", that is ironic.

Most Christians and even Catholics worship on sunday. So I guess they're all wrong?

The first century church did too

I just don't think God is going to say
"Yeah I know you tried your best to be a good person and live according to the Bible but too bad you worshiped on the wrong day.... To Hell you go."

He won't. But neither will he accept someone because they were trying to to one's best.

Well the Bible says if you accept Jesus and believe then you won't go to hell. It doesn't say you go to hell if you worship on the wrong day

In other words it has not yet passed away.

Also we are told there remains a sabbath rest for the people of God and that we are to strive to enter into that rest.