A Kessler cascade necessarily requires the density of shrapnel destroys basically everything in that orbit. Below the density where this happens, it isn't a Kessler cascade in the first place.

You would be forced by (currently around) 2000 tons worth of bullet-mass shrapnel to wait for that shrapnel to de-orbit. Depending on the orbit, this takes months to millenia, because it's determined by atmospheric drag.

The lower the orbit, the better. Starlink's orbits got lowered, this is better vs. that particular issue.