The reason we don't try to convert people, is because Hashem prescribed the gentiles only the seven laws of the sons of Noah. Otherwise, we have an obligation to bring Judaism to people that are not observant. We have no obligation to convert people. We may disprove other religions, but we may not try to convert people. That is why when gentiles want to convert, we try to convince them three times that it is hard. We do conversions, but not so easily, it takes a while.