Building a 3D printer is easy. Getting the details right to build a great 3D printer is hard, as this is where most companies fail. Why?
For example, on this printer, the bed is a three-point mount (two wheels for adjustment at the front of the printbed) and the printer's bed levelling dialogue doesn't show the height difference that needs to be adjusted (which most 3D printers do). It does show how much it needs to be turned, and the bed levelling wheels have 1/8th turn indicators, making it easy to get it perfect.
In short, instead of an arbitrary number like 0.3mm that has no meaning to the user, they tell the user to turn this knob 1/4 of a turn. An instruction the user can follow.
** Why is this so outstanding? It doesn't cost much, but it improves the user experience. Are companies blind to these improvements because the engineers are experienced, or is there a lack of testing during development?**
By the way, years ago I did such a fix/modification myself on a Tronxy XY2 pro by adding indicators on the wheel for 0.2mm height difference so I could convert the number to rotation: https://www.printables.com/model/301670-replacement-bed-leveling-wheel
Because 3d printers are becoming cheap commodities. Those little details cost money and most manufacturers aren't willing to take the profit hit to do anything more than the bare minimum. It's only ever going to get worse at the lower end of the cost spectrum and while higher end printers may get somewhat cheaper, most people won't be able to afford that level of care. The majority of consumer level devices will continue to be just good enough to not get returned but always lacking in fit and finish.
Sadly it is not limited to cheap printer. Check out Thomas Sandlander on the Dagoma: https://www.youtube.com/watch?v=Zys1ZoyvLU8
While this printer is an extreme example other "pro"/expesnive printer have similar issues.