One of the most important things I ever learned about design is that the most important part of design, whether you’re working in print or web or packaging or any other field, is organization. The information you’re presenting has to follow some sensible order. It has to be arranged according to a hierarchy that communicates the appropriate importance of each piece of information, and it has to be arranged in such a way that the viewer knows where to look next.
I’ll say it again: organization is the most important part of design.
Nothing else matters quite as much. Colors and typography matter, sure, and spacing and structure are important, especially since they factor into the organization of the content.
Everything else—sense of depth, animation, etc.—is secondary. Nothing else is essential to good design. Sure, sense of depth can make a site more appealing. It can also make a site look convoluted and distracting. Either way, it isn’t a necessary element of good design.
As long as your content is well-organized—presented so the viewer knows what to look at first and where to go from there—you’ve got good design on your hands.