I really don't think we can take anything for granted. The problem with taking things for granted is that each of us may understand or perceive things differently, so we are all working from a different "zero" or starting point. I also cannot take for granted what the word "quality" means for the same reasons. If I do not know what everyone else on this team experiences as quality how can I prioritize anything? and if I do not fully understand the brand of Wikipedia, which is what your point one is, then how can I focus on one part of quality over another? How do I know which part of quality is the most important or the most important now?
If I do not fully understand Wikipedia's brand in the same way as the rest of the team, then how can I understand or agree to what the structural threats to quality are? For example: if Wikipedia's brand is to include everyone, then policies that ban people only when they engage in really abusive behavior are probably appropriate, and not sanctioning them when they cross the lines of common courtesy and socially accepted behavior might be okay. However, if Wikipedia is trying to be a well vetted source of reliable, neutral information, then anyone that gets in the way of that doesnt belong in the community.
Can you see the shift?
So it's impossible to take anything for granted and get real, meaningful work done.