Starlink adds a tremendous number of satellites to Low Earth Orbit. Like, Starlink is now something like 50 percent of all active satellites. That's a lot of traffic up there. And in LEO, where orbits criss-cross in an endless complex dance, the risk of collisions is far higher than in Geosync. While the advantage of LEO is that everything has a lifetime measured in decades until the orbits decay and they burn up, the risk is Kessler Syndrome, where shrapnel from collisions creates an endless cascade of destruction that makes LEO completely unusable for several decades. That would be the end of all LEO satellites and all manned spaceflight for possibly the rest of our lives. You could still get ships through the Kessler debris layer safely for launching high-orbit and geosync satellites, but low orbit would be too hazardous to place anything in for long-term work, especially since it would risk prolonging the problem.

If Kessler starts, it will be impossible to stop - the shrapnel is too small for satellites to detect and avoid with their adjustment thrusters. A pandemic-style S-curve of destruction as all the satellites in LEO die. And we'd have to evacuate ISS.