According to an article I read recently[1], they measure quality in rate of defects per car produced. According to this, we can get an idea of the scope of the improvements.
As much as I think they are doing a great job and deserve to be there, I've also never seen a car in the $40k range (more 50-60k euros on this side of the ocean) not being "a pleasure to drive" or not having a good customer service.
[1]: https://arstechnica.com/cars/2019/11/customers-rave-about-mo...