Does this verse mean that Latter-day Saints are better than everyone else?

No!

As Spencer W. Kimball said, “No implication is here made that all members of the Church are worthy and that all nonmembers are unworthy, but eternal marriage cannot be had outside of the temple, and nonmembers are not permitted to go into the temple. … Perhaps Paul wanted them to see that religious differences are fundamental differences” (“The Importance of Celestial Marriage,” Ensign, Oct. 1979, 3–4).

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