I've not watched enough of ARI to make an educated evaluation, but I know this Seattle team.
The defensive front is dominate. Williams and Murphy make one of the best DT tandems in the league. If a team wants to lineup and try to run the ball on Seattle they should expect bad results. The Seattle DBs are solid. Woolen's demise is over-reported. Witherspoon is a missile that just needs to be pointed in the right direction. Watching Emanwori (R) and Witherspoon immediately put ball carriers and receivers on the ground makes me smile. That's the thing that makes me most hopeful for the future of this Seattle defense. They tackle well, reminiscent of watching Bam Bam Kam and Earl Thomas do the same thing. It remains to be seen how badly they will miss Jones at LB. I

Jones in the middle of this defense.
Darnold has been exceptional, but I think the starting OTs deserve a lot of credit. Cross and Lucas have been great in pass-pro. Combine being good on the edge with a QB that gets the ball out quickly turns into moving the sticks. I have to say that watching Darnold's quick footwork has been refreshing after seeing Geno Smith hang onto the ball too long. I'm a firm believer that sacks are much more of a QB stat as opposed to an offensive line stat. Seattle has had a reputation for having a sieve of an O-line, but in my eyes it's been QBs that don't get the ball out quickly. Kubiak also deserves a lot of credit for setting Darnold up for success. The five and seven step drops off of play action are allowing Darnold to get the ball downfield. The timing of the play calls have been well designed. Note: Seattle has NOT run the ball well, but they still remain committed to the carries making the play-action effective.
This is a young team. If they can remain healthy and committed to each other they could go far in the near future. I remember the draft classes from 2010 to 2012 and how that resulted in consecutive Super Bowl appearances. The Seahawks have been crushing the draft ever since they sent Wilson away. Seriously, this year's draft class looks like another home run. Emanwori, Arroyo, Horton, and Zabel are all contributing right now. That's four consecutive years of drafting many starters. If you're not sure what that means, go look at your team's last four draft classes. A team is lucky to find two or three starters in each class.
LINK to Draft History.
I tend to be fairly speculative and hesitant to get too excited, but this team has me optimistic.