There are certainly disadvantages.

I live in a very car-unfriendly city that invests heavily in public transport. Amongst other things, this implies that they don't invest in things like car parking space. Most residents don't have cars and cannot have cars because there are far fewer parking spaces in apartment blocks than the number of people living there. Problems include:

1. My wife (who runs a small service business) is constantly having customers miss appointments and explaining it as "I spent 30 minutes trying to find somewhere to park, failed, and had to return home". Being unable to actually use a business at all because you can't park anywhere isn't an issue you see in most cities, but here it happens all the time. You might wonder why don't they just park on the outskirts and take public transit the rest of the way, and the answer is that train stations don't have much parking either, and at any rate public transport is usually 2x or worse slower than with cars (best case), so often they just don't have enough time in their lunch breaks or after work to do that. With a car friendly city, people can pop out to a local business and back in the time they have available.

2. The city is also very keen on recycling. Bin bags are extraordinarily expensive because they are heavily taxed and it's illegal to use any other kind of bag. Fine for small objects, but what about when it's time to recycle something large like a TV or a carpet? The actual solution they push on you: there are special trams that a few times a year park at certain stops, and then you are expected to just carry the full recycling load down there with your arms. You could also buy a little trolley and use that. Is it raining that day? Maybe you're traveling and away from home? Too bad, wait another 3-4 months or so and keep the junk in your apartment whilst you do so. With a car: put the stuff in your boot and go to a fixed recycling point that's always open. Easy.

3. Car-free cities become completely dependent upon the goodwill of their public transit unions, who then exploit that dependency to earn themselves vast salaries and perks. Tube drivers in London can earn more than senior software engineers and have final salary pensions, even though the job is mostly automated and on many lines consists of pushing a button to move to the next station.

4. Transit systems are very centralized and prone to widespread system failure due to poor maintenance, e.g. if points or signaling fail at a busy junction half the city can grind to a halt. Roads are more robust because cars can normally pull over if they have problems, and people can drive around the rare car that's got stuck in the middle. Roads degrade much more smoothly than railways do.

5. Public transit systems invariably run at a loss because ticket prices are set too low for the actual overheads involved. Roads usually raise more in taxes than they cost to maintain.

6. Obviously, there's all the practical downsides that come from not having a personal space like sometimes not being able to sit together with your family, or sit at all.

Don't get me wrong, there are many positives and conveniences but it's silly to say there are no disadvantages to going all-in on public transport. There are many serious disadvantages which is why cars caught on to begin with.