Perhaps the most catastrophic consequence of removing quantum uncertainty would be the instability of atoms
As we understand them, electrons are attracted to nuclei due to their opposite electric charges. However, electrons do not orbit the nucleus like planets around a star; the uncertainty principle precludes electrons from orbiting in definite paths. Instead, electrons exist in an smeared-out cloud of probability around the nucleus. The cloud can change shape and energy when hit by photons or other particles, but for the most part this cloud is unchanging. The technical name for this cloud is orbital and is a specific kind of quantum wavefunction.
The fact that the orbitals are stationary is very important because accelerating electric charges emit radiation (look up bremsstrahlung radiation and synchrotron radiation). Without quantum uncertainty, an orbiting electron emits radiation because a circular orbit requires the electron to accelerate towards the nucleus. This acceleration causes the electron to emit radiation, which causes the electron to lose energy and fall closer to the nucleus. The in-falling electron orbits the nucleus faster and faster, emitting radiation at faster and faster rate until it collides with the nucleus in less than a nanosecond.
If our universe were born without quantum uncertainty, approximately 380,000 years after the big bang, every electron in the universe would have merged with every proton, leaving the universe populated with nothing but neutrons, photons, and neutrinos for all eternity. I don't see how intelligent life could form from such non-interacting entities.