In fairness all those stupid regulations asking manufacturers to reduce C02/NOX etc regularly (Yes we need regulations, but not to an unrealistic level), the technology is simply not there. Yes you can reduce a bit there and there, add a filter up here and down here, but if you look at cars today, they do a little bit better in terms of pollution compared to what they were doing 30 years ago.

My 17 years old 540i designed over 20 years ago does pollute a little bit more than a 2015 M5 with the same engine size. Not that much really.

There is no miracle, run on water, hydrogen, or else to be discovered yet, but petrol/diesel combustion engines doing almost no Co2/Nox emissions, is never going to happen. No way real around it.