The Future of Layout with CSS: Grid Layouts

The problem I have with grids is they don't play nice with fluid resizing. I aim for liquid smooth responses from desktop down to tablet, then just one breakpoint for anything smaller than a tablet. Works for me. Any more break points is a ticket to pain.

What I wish was easily possible with CSS alone, is a method for specific position of an object within a list item, or properties of the list item itself depending on where and how many list items are currently present. That way, if we have 3 list items each containing a thumbnail, the list item could be set to 33% width. If two list items, 50% and so on. Things like a list of thumbs could remain nice and neatly aligned at any point in the responsive page resize. I'm not interested in hacking this with pre-processors, we need CSS to have these tricks up its sleeve. But instead, we get grids?