What you repeat is the propaganda but not the reality.
Out of peak hours and places, cars speed goes reasonably well. Especially if you have to come in or go out of Paris.
But also the mayor administration created a lot of congestion with stupid rework projects like the "place de la Bastille"; closing direct ways across Paris and blocking big avenue to force all drivers to pass by small streets to zigzag.
The air pollution could have been a real reason, but sadly it looks like to not be real: during the worse lockdown, the traffic was reduce to almost zero, and still the air pollution was just reduced of a tiny fraction. Paris is located in a lower part of a big valley, so the pollution is in big part the result of the industries and other of the valley that concentrate there for the most part.
I will not be against a better mix that intelligently reduce the car, for example by having park and drive, big avenues crossing as straight as possible for cars and small streets and blocks dedicated to walk, bicycles, ... Sadly it is not something intelligent like that, that they are doing. A lot of well known urbanists complained about what is done.
The mayor pretends that the changes are to done to have a more vegetal and eco-friendly city, but in reality she is pouring concrete everywhere and doing ecologically bad projects.
For example, she said that she will plant 700 000 trees during her tenure, so far, the net result is at least -1000 trees in Paris.
Also, for example, in honor of the Olympics she built a big fan zone that no one asked, useless, costly, on top of a major landmark, despite the city council assembly voting against the project.
In the famous champs de Mars in front of the Eiffel tower, she built a huge "ephemeral" exposition building for the future Olympics. This took 1/3 of the surface of the champs de Mars Park, but in Additional destroyed the ground by injecting hundred of concrete pillars deep into the soil for this project.
There use to be a free floating shared electrical car service, because of bad contracting they had to kill it.
There was a very good, efficient public shared bicycle system that was well used (Vélib). She decided to renew the contract to go with another provider officially to get some new bullshit features. Now the service is a mess, it did not worked at all for a long time, now it is working badly, with less stations than before, and more costly to the city and to riders than the previous service. This is typical of the mayor administration. The provider even blackmailed the city hall to get more money and the city hall paid...
This is a good example of the real acts of the mayor that despite her speeches are against a good ecological
design. Only at my level, I was used to use a lot the Vélib, and now I haven't used it for a few years because it never worked when I wanted to use it.
For the metro, imagine, having all your trips face to face, ass to ass with other persons. With a micrometer of space around you. Having to fight to enter the train or not sure that you will be able to go in.
Paris is really losing inhabitants, debt goes to the roof, and shop and services are closing. So you can't say that it is just a number of mistakes because it is a continuous work for multiple years.
If you want to laugh, just have a look at the hashtag #saccageparis on tweeter