Guys that create separation and get open faster make it so the QB doesn’t have to hold the ball as long. That’s how they help an average or subpar online.
Also, elite weapons tend to be given a bit more cushion which opens up shorter, quicker throws. And they can take the bubble screens that go nowhere now much further.
In short, you’re not looking at this 3 dimensionally.
But, yes, we’d all like to see the line improved. But not at the expense of a 1st round pick and missing out on elite skill players.
And, because they demand attention, the 'lesser' receivers may get open more.