I really wish people would stop making these claims with only a passing knowledge of the issue. SpaceX’s Starlink in particular has done a good job of addressing these problems because they chose to deploy their constellation at very low altitudes (400-600km) where failures (or debris from collisions, to some extent) quickly deorbit due to atmospheric drag. Their original competitor OneWeb chose a higher orbit, 1000-1200km, to get by with fewer satellites. At those altitudes, the satellites stay in orbit for centuries unless actively deorbited.
Kessler Syndrome is a real risk at higher orbits like 1000km and above. But not at the lower altitudes. Kessler Syndrome is an exponential effect, so if the losses (due to atmospheric drag) are higher than the gain (debris generation due to collisions), then you do not get the exponentially growing debris problem. It’s not even possible.
Although it should be pointed that even at higher orbits and even if you’re technically in the exponentially growing regime, this growth would occur very slowly, not minutes or hours. Think months or years. And it’d take something like an active war with mass deployment of anti-satellite weaponry to trigger that kind of thing.
In fact, most debris problems nowadays ARE caused by debris from anti satellite tests (as well as collisions with old Russian derelict satellites or explosions of upper stages not properly deorbited).
But we also have demonstration missions for deorbiting derelict satellites to prevent the production of additional debris even at these higher orbits.
But sorry to say, none of these problems are due to Elon Musk.
I would prefer some contingency plan so that were not stuck here because Elon decided to go fast and break things...