How do I make onboarding consistent and human as we grow?

You can onboard someone well when it is just you and them. What defeats you is doing that for many people at once without it turning cold and mechanical. You feel the tension: systems scale, warmth does not, or so it seems. That worry itself shows you care about the people, not just the process. Here is the reframe. Consistency and humanity are not enemies. What feels human is often just a few things done reliably: being remembered, being expected, being checked on. You can build those into a system so that every person gets them, whether you are in the room or not. Pick the one moment in onboarding that matters most emotionally, maybe the first day, and design that single moment to feel personal every time. Nail that one, then move to the next. You do not have to make everything human at once. You make one thing human, at scale, then build from there.