The Packers being ranked 30th in average yards to go on third down (8.9) has definitely been a factor in them struggling as well.
That is an important point, but when we break it down (and throw in 4th. down tries) we see an issue below the surface and another takeaway:
3rd and 1 or 2 yards to go: 2 for 7 conversions, 28.6%. 2-6 passing, 0-1 rushing, 0-2 passing at the goal line
4th and 1: 0 for 2, 1 pass and 1 rush, the pass at the opponent's goal line
3rd and 3 - 5 yards to go: 6 for 11 conversions, 54.5%
3rd and 6 - 8 yards to go: 8 for 17 conversions, 47.1%
3rd and 9 yards to go: no plays
3rd and 10 - 15 yards to go: 2 for 16, 12.5%
3rd and 16 - 28 yards to go: 0 for 8, 0.0%
The issue below the surface is poor results on those short attempts on 3rd. and 4th. down. Going 50% at 3-8 yards is a good number.
To your point, there's been a high percentage of long yardage 3rd. downs, with 40.7% of tries having been been from 10+ yards, going 2 for 24 on those 3rd. downs. That's 4.8 drives per game in 3rd. and very long. That's a high percentage of difficult situations.
The takeaway is when we talk about 3rd. down conversions we're not talking about just what happens on 3rd. downs. We're also talking about getting to favorable down and distance, which in the Packers' case so far has been not getting
too close to the 3rd. down marker or goal line.
Sacks and 10 yard penalties are especially drive killers.
Now, a team does not need to convert third downs if they chunk their way down the field and score on first or second down, or hit on big play TDs, or score other ways on defense and special teams directly or indirectly on turnovers and returns to the end zone or deep in the opponents territory,
on any given Sunday. But if we look at the ranking of teams on 3rd. down convertions, we see a correlation:
https://www.teamrankings.com/nfl/stat/third-down-conversion-pct
It's not a perfect correlation, but teams that score a lot tend to be clustered toward the top and those that don't toward the bottom. It's one important aspect of offensive performance and conversely defensive performance in stalling opponent drives.