This is not true, driving in european cities is stressful (narrow streets with irregular layout, high density of pedestrians/cyclists, not enough parking places). The public transit, when done right, is way more convenient.

> would drive if they had free parking, didn’t have to pay tolls, didn’t think it was terrible for the environment, etc

So basically your argument is that people would drive if it weren't terrible in every way? By that logic, people would eat plutonium... if only it were more available, tasted good, and didn't kill you.

That would still make things worse, because cars need roadspace. Getting rid of the road space for cars and making public transit good enough is a pretty good solution.