It's laughably premature to start calling out Seattle's defense, but since it's happening, let's take a statistical look at how the Hawks fared compared to all preseason week 1 performances.
Week 1:
AYN/A: 5.02
Completion Percentage: 59.88%
Sacks: 2.16
Pass Attempts Per Sack: 14.8
INT: 0.73
Pass Attempts Per INT: 43.73
Seattle:
AYN/A: 5.42 (108%)
Completion Percentage: 57.89% (97%)
Sacks: 4 (185%)
Pass Attempts Per Sack: 9.5 (156%)
INT: 1 (137%)
Pass Attempts Per INT: 38 (115%)
The best stat there is AYN/A, which accounts for sacks and INTs. Seattle was a bit below average, something that matches my film study. Simply, for the talent assembled, they didn't play well. But, let's consider, Seattle was the away team, a known and roughly quantified disadvantage. They played in the Metrodome, a stadium that inflates offense. See Seneca Wallace channeling Tom Brady (9.75 ANY/A) or Seattle's overall 9.58 ANY/A. Under Mike Holmgren, Seattle has shown a tendency towards bend but don't break defenses, outperforming their average yards allowed over multiple seasons. And while Seattle certainly allowed some long gains because of bad coverage, it also forced 5 fumbles and allowed only 1.42 points per drive. That's the same as Miami achieved last season, 22nd in the NFL.
So it's not only premature to criticize Seattle's defensive efforts, it's incorrect. They didn't dominate and at times played poorly, but it was a solid effort overall and one that certainly shouldn't alarm.