Back in the day, "Kessler syndrome" was a fairly good way to articulate the fears of many scientists - whose delicate one-off "flagship" scientific research satellites had huge costs and lead times, if things started going wrong up there.
And overall, today's space powers are much more careful about not making messes in orbit.
I see you haven’t read the paper. How long do you think Kessler syndrome is projected to take? How long do you think natural clearing of debris at Starlink’s altitudes is?
Freeways are not 3 dimensional and they don't have an automatic cleanup that cleans up things within a pretty short time. Also area we are talking about is fucking gigantic. Also accidents are going to be very rare as sats deorbit themselves end of live and even if they break and can't move anymore, other sats that can still move can evade them.