And all of those top lawyers were once clerks and junior staff, who learned their craft by doing the grunt work.
This is going to be a problem.
Junior lawyers will still have plenty to do.
The path from passing the bar to being a successful / well-paid attorney has been extremely difficult for a decade now. AI will simply continue this trend.
I think you're heavily discounting the fact that searching through case law is not just "type in words into LexisNexis", but it's searching, parsing and consolidating case law that is relevant for a Partner. You actually read the case law, spend time understanding it, and build a report around it.
Yeah it's not a skill that everyone can do, but once trained to do it there's no point only doing that same task over and over because you won't advance your skills in other aspects of the field.
Every case has its own unique characteristics. It's not just doing the same thing over and over again.
But at the same time not all of them require law degrees either, many para-legals and helpers aren't full lawyers.