Circumcision was part of the specific covenant with Israel that confirmed them as God's "chosen people", chosen to serve as an example (both good and bad) of what happens to a nation when it does or does not follow God's rules.
Christians are generally agreed that this requirement is not binding on anyone else other than those that are part of the "old" covenant.
On the other hand, the Sabbath Day was established at creation:
Then God blessed the seventh day and sanctified it, because in it He rested from all His work which God had created and made.
— Genesis 2:3
Notice that it was the day itself that was sanctified.
God created the Sabbath Day as intrinsically different from the other six.
The Sabbath Day is explicitly listed as one of the Ten Commandments.
Remember the Sabbath day, to keep it holy.
Six days you shall labor and do all your work,
but the seventh day is the Sabbath of the LORD your God. In it you shall do no work: you, nor your son, nor your daughter, nor your male servant, nor your female servant, nor your cattle, nor your stranger who is within your gates.
For in six days the LORD made the heavens and the earth, the sea, and all that is in them, and rested the seventh day. Therefore the LORD blessed the Sabbath day and hallowed it.
— Exodus 20:8–11
Notice that it is "the Sabbath of the LORD", not "of the Israelites".
Notice that one must "keep it holy", not "make it holy" or "treat it as if it were holy".
Notice that God "blessed the Sabbath day and hallowed it" at creation.
God's covenant with Israel did require that they obey the Ten Commandments, but those commandments weren't written explicitly for Israel as part of their covenant.
The Sabbath Day was made holy at creation, and the Israelites were expected to recognize and respect God's special day.
"The Israelites are to observe the Sabbath, celebrating it for the generations to come as a lasting covenant.", but that doesn't mean that only Israel must follow God's laws.
Many people today as part of their jobs are required to swear to defend the constitution, or to uphold and obey the law, or …, but that in no way implies that other people are not expected to do the same.
God wants everyone to obey his commandments, with covenanted Israel serving as an example of what obeying them means.
The Sabbath serves as a sign that one is following God's laws.