Which "Christianity" are you talking about? The one with Pope's, Cardinals and Crusades? No, we do not believe in that "Christianity."
We do agree with many of our "evangelical" brothers and sisters who love God, the Messiah of Israel and the Bible.
We do not agree with all of "Christian" history. And to go a step further, we do not believe that all who have claimed to be "Christians" were.
Let's define the term: Christian equals a person (Jewish or Gentile) who follows "Christ". In Hebrew, we do not say "Christ" but the original Hebrew was "Messiah" or "Moshiach" which means "anointed One." One who was chosen by God for a very special task.
So a “Christian” really should be someone who follows the Jewish Messiah. So when you say "Christian" - you are really saying you are a Gentile who follows the Jewish Messiah or "Christ" in English.
And a Gentile can follow Him - and should!
So a person can be Jewish or Gentile (but not both).
A person can be a follower of the Messiah (called Christ) or not and that does not stop him/her from being Jewish or Gentile.
We are Jewish by birth, but came to believe years ago that Jesus (Yeshua in Hebrew) is indeed the Jewish Messiah.