It's not relying on a WR to make miraculous catches, in the sense that they couldnt produce or be effective without it, but it brings another dimension to your offense. We're talking about the type of WR thats open even when he's not. The type of guy that when it's 3rd and 8 in the 4th qtr and the D has 7-8 guys dropped in zone and there's nowhere open to go with the ball, that'll demand the ball no matter what, go up and get it.
The guy that dominates in the red zone. A guy that makes 50/50 balls 75/25 or 100/0.
When you have that guy.... no you dont have to rely on it, but when you know he's capable of doing that 1-2 times a game then you have confidence when the games on the line and maybe take a chance you wouldnt have otherwise. You dont need to see as big an open window when throwing his direction to have the confidence to rifle it in there.
And hes not talking about throwing bad passes over a guys head or forcing diving catches. We're talking about the when the WR's running a crossing route or slant, instead of having the perfect precision that hits him in stride without breaking pace (like Brees, Brady often do) maybe misplacing it a little bit so that it hits him right in the numbers instead of out in front of him... so he has to slow down a bit and maybe box out the CB's arm trying to make a play to break it up.
Also, there are times when you just cant throw the perfect ball. The D plays great coverage and the typical windows just arent open.... and maybe you have to place the ball a bit high, down low, or behind him -- a spot where the DB cant make a play but you give the WR a chance to.
Regardless of how good a QB is, these types of plays/situations present themselves A LOT in the course of a game. Especially with a QB like Joe who's best asset isnt perfect accuracy on the short/intermediate stuff... but absolutely can make the impossible throws or fire a ball into the tightest of windows 15-20 yards down field.
So, theres nothing wrong with thinking that this team is missing that type of guy. The one who can make the body adjustments to available in those small, imperfect windows.... the one who will go up high, down low, reach behind, box out, or take the hit and still secure the ball. The one who knows hes open no matter what the Defense does.
Ross can be and very may well be a play maker. But he doesnt present those qualities. Perriman might learn to offer some of that, but mostly down the field -- not in the traffic and over the middle. Wallace doesnt offer those abilities.
We have big play ability. We have guys who can take a 1 yd pass and turn it into an 80 yard TD. We have guys who can get open 15-20 yds down field with speed. With Ross we have more of that, maybe even better of that, but we dont have what we're missing in those tight, crunch time situations that often decide games.
And if you want to be a ball control, balanced, physical running team... then you almost NEED that missing element. Because you're going to put yourself in a lot of 3rd and 4's with the blitz raining down where Joe will have to just fire a ball to a hot route that may or may not be open and just trust he'll catch it. We're going to be in some close games thatll come down to needing a TD from the 15 yd line with time expiring, and needing a guy that can fight through the crowded end zone and catch the ball while taking a big hit.... or when needing a FG to tie in the 4th while at the 50 yd line and needing 15 yds to get into FG position, the guy who will get to the boundary and let Joe just throw it over his shoulder while he boxes out the CB and makes the catch falling out of bounds.
Joe's biggest strengths are his arm, getting the ball deep, making throws others cant all over the field, and being BIG TIME when the game is in the balance. We need a WR to match those qualities. It's obvious that his best connections have been with guys who showed him those qualities (Boldin, Pitta before injuries, Heap, SSS). And Mike Williams is the epitome of that.
John Ross, for the good qualities he does have, he is not that.