Here's one way of thinking about the needs at WR in terms of production.
A very successful Aaron Rodgers season probably looks something like 365 completions, ~4200 yards, and maybe, say, 38 touchdowns.
So what are realistic estimates of production for the guys currently on the roster?
Aaron Jones: 60 receptions, 480 yards, 4 TD
Allen Lazard: 50 receptions 650 yards, 6 TD
Randall Cobb: 40 receptions, 480 yards, 4 TD
Robert Tonyan: 35 receptions, 420 yards, 5 TD
A.J. Dillon: 30 receptions, 240 yards, TD
Josiah Deguara: 25 receptions, 250 yards, 2 TD
Marcedes Lewis: 20 receptions, 200 yards, TD
Amari Rodgers: 15 receptions, 150 yards
So those estimates total up to account for 275 completions, 2870 yards, 23 TD's.
So if that's close to accurate, you need to find about 90 completions for 1300 yards and 15 touchdowns.
That obviously doesn't need to be one single player-- it could be a combination of options that are acquired via trade, FA, or draft.