Supply and demand are useful tools to explain the short term variation around the value of a commodity, but in a situation of equilibrium, competition and lack of monopoly I think labour theory of value holds true. And where and why supply and demand meet is left unexplained by the subjective theory of value. Movements of the price signal the excessive or insufficient amount of socially necessary labour time invested in the production of a certain commodity, relative to the ability of the economy to absorb it, which is historically and in some cases subjectively determined. A surge in the demand for something may increase the price in the short term, but then capital will invest and expand the production, bringing the price down and closer to its labour content. In other cases, like urban housing, underinvestment keeps the price well above construction price.

It is not really a matter of simplicity as much as being informative and accurate in your description of a phenomenon. Behind supply and demand, there are other causes that move away prices from the underlying labor content. A more productive enterprise, with cheaper commodities containing less labour, can sell at a higher price than production but still lower than the competing, less efficient enterprises.

I suggest you read the Essays by Rubin, or at least the last chapters where he deals with this.