Stu, ignorant = without knowledge. It is not a value judgment, it is a description. Your plant-knowledgeable example may well be ignorant of smartphones, but they might not. I have a doctorate in my field and *I*'m ignorant when it comes to smart phones. In fact, today I had to call the sales people to ask how to not answer the phone, I kid you not, because I kept sending a robot to voicemail.

In my experience, Americans who went to public schools tend to be extremely ignorant.

The people who marched with torches through my town are uncivilized *and* likely also ignorant, but I won't use ignorant as an insult for them for being bigoted assholes.