The challenge isn't modern diesels its the EU4 and EU3 diesels that are the big particulate and NOx emitters
And they've completely ruined the demand for people replacing these old ones with new clean ones by demonising diesel. So instead people have hung into the old polluting examples as they don't want to risk a new diesel but don't want to give up the fuel efficiency they currently have.
I drove a new LCI 6 cylinder 5 series diesel with mild hybrid tech a few months ago. It was ultra smooth, very fast and super efficient. But I wouldn't want to risk putting my own money into one.
Nice one.