It is not selective. Jesus is rather consistent in interpreting the commandments in a more spiritual way than a purely legal one.

If you follow the letter of the law, for example, you are OK if you don't outwardly break any of the commandments. This is how a Prosecutor sees it.

However, Jesus teaches in Matthew 5 that if you you even think about breaking the commandment, you have sinned. For example, He expands on adultery and murder to include motivation and intention. Jesus was more concerned about what is in our hearts as sin originates in the heart. Sinful thoughts and desires can lead to sinful actions. This is not explicitly written in the commandments. This is how a judge sees it, and one assumes Jesus is the ultimate judge.

Judgement is extremely important, particularly in the commandment against murder as written in the original Hebrew, which is the intentional and unjustified taking of a human life. It's not a blanket prohibition against killing as we have taken it to be. But what's justifiable killing? Suddenly it's not so black and white. Does this mean Jesus was all for killing people for justifiable reasons? I don't have an answer for that one. But a strict interpretation would require accepting that.

Although not commandments, Jesus also addresses other matters, such as eating pork in Mark 7:18-19. Jesus teaches that it is not what you eat that defiles you, rather what comes out of your heart. Again, He teaches us against ritual purity in favor of inner purity and intentions.

My overall impression is that Jesus freed us from the superfluous rites of Judaism so that we could focus on the more spiritual aspects of our relationship with God. He does't do away with observation of the Commandments. However, he gives context to help us avoid being wicked in hour hearts (spirit of the law) even if we are not wicked in our actions (letter of the law).

This is just what I get out of reading into it.

However, as a Catholic, I defer to the Catechism, which lays out the reasoning for the Church choosing to celebrate Sabbath on Sunday.
https://www.vatican.va/archive/ENG0015/__P7O.HTM

Some of this is addressed in Hebrews 4.

9 There remains, then, a Sabbath-rest for the people of God;
10 for anyone who enters God’s rest also rests from their works, just as God did from his.
11 Let us, therefore, make every effort to enter that rest, so that no one will perish by following their example of disobedience.

The passage is about Israel's disobedience and their denial from entering the land that was promised to them. But the passage is more about the new faithful entering the Kingdom of Heaven, which is promised if you are obedient. Thus, we are not absolved from observing Sabbath. But the rules aren't so hard like Moses had. In Hebrews 3 it is declared that Jesus is greater than Moses. Jesus does not have the same limitations that Moses had.

Therefore, we believe that this spiritual rest in Christ supersedes the physical rest of Sabbath. However, it does not free us from observing Sabbath completely. Rather, it moves Sabbath from being a purely physical act to a more spiritual act. This is also how we observe the Eucharist, which is a re-enactment of the Last Supper. Rather than sacrifice an actual lamb, pour its blood on the altar, and eat its flesh, Jesus provided us with a more spiritual option with his sacrifice in which his blood and flesh are sacrificed in the form of wine and unleavened bread.

This gets into the Catholic weeds a bit as the Eucharist is central to our relationship with God in fulfillment of Jewish tradition and also The Wedding Feast of the Lamb from the Book of Revelation. As Christ rose on Sunday, we celebrate his resurrection with the Eucharist, which is a symbol of God's new creation and our redemption. As we are "at rest with Christ", it fulfills the observance of the Sabbath on Saturday.

As far as I can tell, the Church does not argue that Sabbath is not on a Saturday. Rather, rest on Sunday, which coincides with the Eucharist, satisfies the requirement. When it comes down to it, Saturday is observing God's original creation, and Sunday is celebrating God's new creation and covenant.

Certainly, you can observe Sabbath on Saturday or Sunday. Or you can observe both, if you are so inclined. It's just that for us it's more of a spiritual observance of Sabbath, which we are still required to have. So it's not like we're getting away with NOT observing Sabbath. We're just fulfilling the Commandment in another way.

That's just Catholic catechism. I don't know how other Christian denominations work that out. But I think the overall premise is that Christ made faith and salvation more accessible.