That's a fair point but from the top 10 law schools POV, they have no incentive to care about this. On the flip side, this is the sort of self-reinforcing feedback loop that allows top ranked schools to collect the best talent (or at least the kind of specific students that have the capacity to grind in the way that is necessary to succeed at Big Law firms).

If the new hires arent up to par, then this is something the the law firms should be incentivized to address. Since hiring practices generally haven't changed over the last 20 years, I'd guess that hiring from top law schools is perfectly fine (and maybe that is an indictment on the nature of work that happens at law firms).