"Form follows function" is a phrase that many people have heard before, but what does it really mean? In a design sense, this means that the space and its furnishings have to be practical, first and foremost, before you ponder their look and shape. This is especially important in the bathroom considering the space is perhaps the most utilitarian of all rooms in the home.
Sticking to this ideology means understanding the uses of your bathroom accessories and fixtures. The bathroom vanity's main purpose, for instance, is to allow people to wash their hands and as storage. If the furniture prevents you from doing these things then it's not a very functional bathroom vanity - no matter how beautiful it might be, you should consider other options.
If your bathtub gives you backaches every time you soak in it, then it's practically defeating the purpose of having one, no matter how it looks.
When renovating your bathroom and looking for fixtures on the market, just remember to search beyond the aesthetics and see them for their practical applications in your space.