Somethings become very complicated in constraint based systems and they are often much slower in my experience than more special purpose layout systems. That said i'm not against constraint systems either, they just both have their place.

You clearly know your layouts :). I agree, AutoLayout is the most powerful system I've worked with.

I wish others would start their layout systems based on it (others like React Native, or native Android), then add simplified APIs like flexbox using it if needed/desired.