alt Hacker NewsKessler Syndrome is the biggest dealbreaker. We're already fairly far advanced in that scenario from Starlink, and competitors/scaleouts to Starlink promise to be worse.
If you plug eleventy trillion dollars of hope that the aristos can finally replace the working class into the issue, Earth loses access to low orbit from orbital debris almost immediately.
Their entire mindset cannot deal with this. Low orbit is a physically-enforced type of commons, inextricably tied to tragedy if overpopulated. You cannot privatize it and scale indefinitely. There is no defense, and any pissed off individual actor who gets malicious can burn it to the ground.
Starlinks are in low enough orbit to passively decay in less than 5 years, that really can't meaningfully contribute to a Kessler syndrome.
Chinese mega constellations on higher orbits & their spent stages left in space are a bigger issues.
Still in case it got going & made higher orbits unusable, starlink would likely still work just fine on the lower self-cleaning orbits, not to mention using a partial (and hopefully soon full) RLV for replenishment.