There is an enormous amount of engineering and technology that goes into pollution control on modern diesel engines. The list of failed engines is proof of that.
That said it is highly unlikely that Detroit, Cummins, and other manufacturers are going to redesign an entirely new engine, which could possibility be
ready for use in a couple years, only to have it become illegal two years later.
As for the fuel consumption issue, only someone who never put fuel in a 318, a big cam 350, a Mack,or 3406 Cats would think that fuel mileage was better in "the good old days". That, and imagine the "smoke black as coal" blowing around in major metro areas? You couldn’t read the exit signs!
We used to change oil every 10,000 mi. With the newer engines my 2010 DD13 oil change was factory recommended at 50,000. Which I did with no problems. I have been told they have raised that to 75,000? That’s a considerable reduction in normal maintenance cost.