It's hard to imagine so many people having had issues with intake valve deposits.
It happens to them all eventually, some worse than others. Most don't care to look and the vast majority don't know or care. By the time they appear in some vehicles, they have already moved on to another car. For those that keep their cars a long time, at some point it will become an issue and reveal itself in the form of loss of MPG and rough idle.
Walnut blasting, using a good oil, reduced drain intervals and using a good cleaning service such as ATS are the only things you can do.
Ideally, don't buy a GDI engine. LOL. Stick to a mixed setup.