It took a long time for python 3 to add the necessary backwards compatibility features to allow people to switch over. Once they did it was fine, but it was a massive fuck up until then. The migration took far longer than it should have done

Its widely regarded as a disaster for good reason, that forced some corrections in python to fix it. Just because its fine now, does not mean it was always fine

Now they just break stuff every release so we never relax.