That is why Hashem caters for the superior Noahide who wishes to formally affiliate to the Jewish People & to take on some mitzvah observance, but who is not up to the strictures of full conversion to
Ger Tzedek status, in the 46-times in Torah mentioned lower level
Ger Toshav status = the
gercha asher b'shaarecha - "your ger who is in your gates".
In the Biblical era, marriage to some Ger Toshavs did occur.
Today it is not allowed.
A Ger Toshav is not a Jew; but like an Eved Knaani, is not a regular Gentile/Noahide either.