Density functional theory is still quantum mechanics, but operating on the expected electron density itself, rather than the many-body problem of all the electrons. It's pretty good, but not fast - around a CPU-minute for a medium-sized molecule.

I'm working on approximating the electron density using just the nuclei positions and some neural networks. The throughput is tens of thousands of times higher than for DFT. But since the model itself contains little or no physics, the training data has to be very clean and complete.