Good culture fit is when we ask an employee to do something and they do it. A bad fit is someone who occasionally says no. A toxic employee occasionally says no and explains why they won't.
I've always thought being meek and obedient was part and parcel of working for someone else. But I think being a good culture fit is a bit more than that.
They should be expected to have an opinion and allowed to express it. If you don't want any of your ideas challenged ever, then don't waste your money hiring a person with a brain. And if you hire someone with 10 years of experience, hopefully you can appreciate that they've learned something in that time that give them a perspective you want to hear.
But, of course, after they've respectfully disagreed, they should also be ready to set aside their opinion and go along with whatever was decided. That comes with the professional part of smart and professional.