Page "Supergravity" Paragraph 21

Initial excitement about the 10-dimensional theories, and the string theories that provide their quantum completion, died by the end of the 1980s.

There were too many Calabi-Yaus to compactify on, many more than Yau had estimated, as he admitted in December 2005 at the 23rd International Solvay Conference in Physics.

None quite gave the standard model, but it seemed as though one could get close with enough effort in many distinct ways.

Plus no one understood the theory beyond the regime of applicability of string perturbation theory.