Earlier quoted context omitted.
Well, you say you're skeptical of taking advice from a domain expert, but then you list a lot of, apparently, domain experts you want to hear from. I agree with the latter sentence - I want to hear from a lot of people with narrow expertise and different perspectives on anything important, but I probably don't care what a generalist thinks, because why should they be better at synthesizing the experts than me?
If you want to take on the cognitive load of being the generalist for everything, all the power to you! For me I pick and choose. I pretty much leave my car and rooftop to the experts but I dabble in electrical, plumming, carpentry, landscaping, etc. Etc.
Your second sentence is about when you defer to experts and when you don't, so apparently you too are your own generalist.
There are no "expert generalists"! If you wanted one, you'd need an even more general generalist to choose which generalist was trustworthy...