For someone who joined at the peak of September 2021, let's assume an L6 offer of $240k + 20% bonus + $1.1M in joining stock over four years. With no stock movement and meeting expectations, they'd make $298k cash + $275k stock, for a total of $563k. Now, with that stock down by 50% (ish) as of today, they're total compensation would be $436k. That's still a serious chunk of change, and while a $138k drop in compensation is nothing to sneeze at, they'll also be getting a new grant of $220k/4 years this month(ish), and every year hereafter, bringing their 2023 compensation almost back to $500k if the stock market doesn't move.
So yes, it's a serious pay cut, but it's still amazing pay. Now, if they were bullish on the market, then it might make sense to try to move to another company that can come up with a 7-figure joining bonus and ride that appreciation to new stock heights.