We had bona poly applied in august right before we moved in. I've vacuumed weekly but have never mopped until today. 6 months without mopping and the mop water stayed almost clear as it came out of the tap.

Is this normal or does it mean I'm just not getting a deep clean?

There are 4 people living in here and no one removes shoes either.

I wouldn't wet mop a wood floor. However, it sounds like you are keeping the floor clean with dusting and vacuuming, given the mop water remaining clear. I'd stick with that and forego the mop.

FYI, myself I like a no shoes policy. The street is a dirty place.