According to the Talmud, all that’s commanded of the non-Jews is to follow the Seven Laws of Noah.
Don’t worship idols, don’t curse G-d, don’t murder, don’t commit adultery/sexual immorality, don’t steal, don’t eat a living animal’s meat, and have just courts.
If that’s enough for the non-Jews, then why is it not enough for the Jews?
It’s hard for me to imagine someone who’d say “I’m not Jewish. I don’t believe the Torah is divinely inspired, but I’ll nevertheless follow these seven rules because the Talmud says so.”
I think the point of these commandments is that they’re the most important, which is why Hashem wants everyone to follow them. What’s good for the goose is good for the gander.
I fail to see why Hashem wants the rest of the world to follow seven rules, when the lucky Jews get 613. According to the Talmud, something as simple as eating a cheeseburger on Friday night is perfectly acceptable for a Muslim or a Christian to do, but a Jew who does the exact same thing has violated who-knows-how-many mitzvahs.