yes the problem is well known from former times, when dealing with GUIs on TVs with CRT monitors...
Nowadays, the problem is rare - as far as I know most of the TFT displays are providing almost rectangular pixels. Of course, there are exceptions, e.g. the Raspberry Pi display has a pixel aspect ratio that is not 1:1. As a result, a circle appears as an ellipse.
In this case, it is necessary to be aware of that during the UI design and to create bitmap images that are compensated - especially, when circular objects are shown.
Any scaling during runtime would cost a lot of performance and result in a partially unsharp result.