Because the last several years they had needs on defense defense and defense.
And yes....Rodgers covers a lot of that up on offense. But they also brought in Oline...and part of why is that there draft picks on D did not pan out...but on offense they hit on guys like Linsley, Bahktiari, Tonyan, Adams, MVS (to a degree there...deep threat), Jones, Williams, Jenkins...
Where they whiffed had been at corner, safety, DL, OLB, ILB. PRetty much all over the field on D they missed high draft picks. So they had to bring in Amos, and the Smiths...
Adams was a 2nd rounder...prior to and with him they have had Nelson, Cobb, Jones, Jennings (2nd and 3rd rounders). Yes...even later round WRs can catch too (sometimes). THey scatter shot it in 2018 with MVS, JMon Moore and EQ...likely hoping one pans out (similar to how Ron Wolf drafted).
Though...I would agree...they should have drafted a couple more over the years (especially given their success in 2nd round WRs). I don't know what their boards looked like in other years when they took a guy like Josh Jackson in the 2nd. Apparently they tried last year to trade up...but were unsuccessful (or maybe that was smoke screen). Ultimately that failure to go up and get Jefferson or Aiyuk leads them to Jordan Love and the mess we are in now.
I just think its a laughable thing to say they don't pay to retain their own guys...their philosophy has long been to retain their own. I also think the "he has no weapons" is an overrated and easy thing to claim...but ultimately doesn't hold up to scrutiny.