The issue is not what Wuerl knew about McCarrick, the issue is that Wuerl was previously in charge of a different diocese where he has been accused of, many years ago, not removing abusers from active ministry, or not removing them quickly enough.
It should be relatively easy to find a replacement, perhaps a younger man, who isn’t featured in some grand jury report for being soft on child sexual abusers.
It’s true that the PA grand jury report was a bit of a hatchet job on Wuerl because at some point he saw the light and later went all the way to the Vatican to insist that an abuser in his diocese not be returned to active ministry, but of course the report features the negative things he did, not the positive things.