I tend to be a rationalist religious Jew, and try to contextualize the mitzvot and make them meaningful to my modern, western self.
But there's one mitzvah that defies contextualization or reinterpretation.
Standing alongside the mohel at my son's brit recently. I realized that there's no way I would be doing this were I not living the life of a religious Jew. It's an ancient ceremony that may or may not have medical benefit. But a roomful of people sitting there celebrating as a helpless baby's genitals are cut? It really does seem barbaric and bizarre.
I've adjusted my Judaism to my doubts about most of the ikkarim and made it work for me. But with brit milah, I just had to let go of my modern mind and accept that some things in Judaism cannot be rationalized. It's an ancient mitzvah that smacks us in the face and says to us that choosing to live as a Jew means accepting that not all of Judaism is rational. Rather, we do it as part of avodat Hashem, and because it's the continuation of a chain of numerous generations of my ancestors.