You're right that cars aren't going away, and I don't think it's a serious goal.

The point about equilibrium you're not thinking through fully. If you'd have the 20 minute commute with no traffic and parking right in front of whoever you're going, everyone would do it and you'd just wind up with, well, not that.

But as transit* improves you are able to do more with less, and instead of spending insane amounts of money on 5-lane highways and McDonald's for all and the extractive economics that come with that, you can maintain your existing infrastructure and give folks who can't, shouldn't or would prefer to not drive the option to get to whoever they are going without doing so. That frees up the existing highway infrastructure a little bit, reduces costs across the board, and has a lot of other nice benefits.

You are effectively arguing against other transit methods and models because you'd rather sit in traffic, because without the introduction of alternatives that's what you are advocating for - again because everyone will be in the car and you'll never alleviate traffic and you'll never have a 20 minute commute with free and easy parking.

* We should move away from the "public transportation" frame of reference. Highways are public transportation too, fully funded by taxpayers (in general, it maybe be uniquely different in some countries) and are an entrenched lobbying group that justify projects at the expense of the public too.