I don't think Justin Fields is a terrible quarterback and I've long maintained that it is entirely appropriate to withhold judgment on what to do in the draft until after the entire season is over. So yes, the Green Bay game matters, and it obviously has outsized importance because it's the Packers and its a whole thing.
In most QB stats Fields is in the ~20-something range of starters. That doesn't look spectacular. I think he's gotten better after he came back from injury, but he's still been inconsistent. I think, on the whole, factoring in his legs and his field awareness and his propensity for insane plays nobody else in the league can make, he's currently about an average NFL starting QB (with the potential to be better than that, but also perhaps a ceiling that is below 'elite'). Is that enough? I dunno. If I was a cold-blooded NFL executive who didn't want to factor in what it would do for the locker room, what the salary cap situation looks like, the coaches, etc. etc. - probably not.
As a fan, I'm a reactive moron who swings up and down based on the irrationalism of football wins and losses. I was stoked to watch the Falcons game. If he beats the Packers resoundingly I'm sure I'll be a gigantic homer and feel significantly more reticent to trade him. It is what it is.