I think the problems with modern cars' styling are the use (overuse) of creases in body panels and false intakes/vents. Manufacturers seem to be obsessed with aggressive styling for all types of cars, the Mercedes A-Class is a typical example:
That isn't even the AMG model. Here we can see unnecessarily large intakes (some blanked out) at the front, along with heavily sculpted door panels and a strange splitter/lip at the front and side. In my opinion this is too angry looking with too much going on, therefore quite ugly. Though to many people it looks quite sporty, which can be seen as a positive.
Along with Mercedes, there are plenty of other manufacturers that over-style their cars. Lexus is probably the worst offender.