Qwert, you’re right that it is not the job of a kiruv rabbi to give fiery mussar shmuzen. That’s true. It doesn’t mean that a rav’s job of an observant community is to be a role model.
Rav millers shul were all orthodox from the beginning. He was a kiruv person, but kiruv krovim, bringing closer people who are already observant. Those people do need fiery drashos, and at the very least tochachah that they’ll be open to.
Being a kiruv rabbi in a shul or a college is different, and I’m surprised you can’t see the clear difference.