To be honest, a couple of your dealbreakers would be dealbreakers for me. Not the thing you mention itself, but rather, your having it as a dealbreaker.
Walking slowly? What if someone is unfit or has a disability or simply enjoys a more leasurely pace? I would wonder if the person who can't tolerate a slow walking companion is impatient and intolerant of natural and harmless human differences.
Not getting along with family members? Some people have bad family members, and relieving themselves of that toxicity by having limited contact can be the most healthy thing to do. Someone who does not understand that must've really lucked out in the family department and perhaps lacks empathy to understand the difficulty of some relationships.
Some other dealbreakers of mine:
Negging. A sort of "Play it mean to keep 'em keen' approach. One time I was having some flirty banter with someone, but they kept throwing in jokey insults and put-downs and I noped out of there. Nope.
Being a crazy Republican type
Not being open to a vegan lifestyle / not having animal rights as a primary concern in life
Treating service people badly
Lots more. I want a nice and kind person, be it in a friend, family member, partner, colleague.