The Christian interpretation of Judaism is a bit silly, because they project so much:
Judaism doesn't have a concept of hell, or Satan as an enemy of God, or the necessity for people to be absolutely flawless (while simultaneously asserting that being flawless is impossible) - just to mention a few profound differences.
So when Christians start posts with "as a Jew, you have to keep ALL the laws and NEVER FAIL EVEN ONCE or else be DOOMED TO ETERNAL DAMNATION", you know they've never so much as talked to a pious Jew.
Judaism is not a religion you typically convert to. Like many others in the near east (Zoroastrianism, Mandeans, Yezidi, etc.), it's closely linked to ethnicity: this is why being Jewish is both a question of religion AND a question of family trees.
That said, unlike with the other examples mentioned, it IS possible to convert to Judaism. It's just not a proselytizing religion.