I enjoyed your post. Especially your response to shapes, balance, play. Even your analogy to the child playing with blocks.
One of the most exciting, powerful, and rewarding experience in painting is arranging the shapes of things; playing with balance, rhythm, and positive and negative spaces.
Many abstract artists have limited themselves to this aspect of art, Kline, Rothko, and Kandinsky. And have contributed a great deal to our understanding of the importance of negative spaces in composing a painting.
Many contemporary representational painters have adapted this knowledge and have brought new ways of composing representational art. This will be one of points in my upcoming lecture on innovation in art that I am giving next week in Vancouver at TOC's Summer Conference.
One of the distinguishing conflicts between abstract and representation art is: paint representing its self vs. paint as a means to an end. There are many people that, who know little about art, think that such concepts are an intellectual game but the experience of actually painting and dealing with this issue has profound and personal consequences. Notably painters like Rembrandt and the French Impressionist stress the properties of the paint and use it as a means to an end; masterfully matching the end and the means. Conversely, abstract art cannot do this--the means are the ends.
The possibilities in painting (and I am sure Peter can enlighten us on the vast possibilities of architecture) are amazingly broad and are not limited to the following:
Great representational painters have integrated all the above while pure abstract artists specialize in an area(s) and sacrifice other aspects. For example, Pollock, has no form, light, anatomy, perspective, or subject matter (I base the last on the logical argument that your means, paint, cannot also be your subject matter).
Rand is completely consistent in her focus on the pursuit of the possibilities of art and not artificially limiting its nature.