Is ending all new gas and diesel cars and trucks a good thing worldwide?

In some ways this is good. However, unless you protect drivers and passengers and bystanders from Electrical Coronas around large electric generators and large electric motors in use you are going to create other problems. Even though air might get better so you don't see smoke or smog in the air everywhere, you would make millions of people sick from Electro-magnetic unshielded radiation and it's health effects on everyone.

So, unless you address the electromagnetic radiation and it's short and long term effects on everyone exposed (especially young children now in all electric and hybrid vehicles) you are going to have a nightmare of health problems just like we did with leaded gasoline with thousands to millions of retarded minorities in large cities where they were exposed to burned lead in gasoline from the 1920s until the 1970s all across the U.S.

It's relatively easy to address this problem for passengers and drivers by the way. Lead shielding of various thicknesses could theoretically protect drivers and passengers from short and long term health problems from ongoing exposure to electromagnetic fields from electric motors in operation and electric generators in operation. However, a lot of testing and likely thousands of dollars per vehicle would be needed to make them safe enough for children to ride in the next 30 to 40 years without getting cancers or other neurological problems.

On a positive note by not burning gas or diesel you also allow oil then to be used ongoing for making plastic which we are going to need for thousands of years or more into the future.

If all oil is gone making plastic will be much more difficult on into the future.