The change won't be for free. But rather than lower the usefulness of cars, make sure new cars have better fuel economies (which directly translates to lower pollution). Within 10-15 years, clunkers get replaced anyways, so a general policy of "by 2027, all newly-registered cars must have a maximum amount of X litres per 100 kilometres" or a ban of Diesel engines outside of speciality markets (military, agriculture, trucks) would hurt virtually no-one (but inefficient car makers, who should improve).

If you hit the poorest, you won't get a ecological paradise, you'll eventually get the next iteration of an autocratic dictatorship (either left-wing or right-wing) - now with the extra support of the industry. No-one needs that.

You clearly don't understand the urgency of the matter. Maybe if you wrote "by 2027, all newly registered cars must have a maximum amount of 0 litres per 100 km". Cars, of all sorts, is fundamentally unsustainable in urban areas. They take too much space, they forces spread, they are too loud, they use too much energy and they polute too much (that includes electric cars). So we have to lower the usefulness of cars to make our cities more useful for the people that live and work in them.

(Electric cars might be the best alternative in rural and even some suburban areas. But they don't belong in a city.)

The reason diesel engines have been prohibited in certain city centers is because they have been shown particulary bad for people's health [0]. That is usually also something that hits the poorest people hardest. Rich people choose to live somewhere else.

Your last paragraph is just non sequitur. If you want to, you can try to explain why you think that would be the case.

[0] https://www.theguardian.com/environment/2017/may/15/diesel-e...