Sure. But past success, given a large enough sample size, is also who you are until proven otherwise. Similarly, each season has unique circumstances, so you'd have to evaluate those seasons within that context. For example, has Seattle had the more talented team and underperformed in the playoffs? I can only think of one example that might fit that description: the Rams game in 2020, arguably the worst game of Russell's career.
Seattle's been in one of the toughest divisions over the last decade. And they've made the playoffs consistently. Making the playoffs invariably means Pete's an above-average coach. Fans are entitled to hold him to whatever standard they like. However, predicting the team will fail for X, Y, and Z reasons and getting it right occasionally is not proof of good analysis.
Why? I've mentioned this before, but I'll repeat it. If you predict a team won't win a playoff game with coach X, you have a 78% chance of being right without doing any analysis. So you could predict that coaches like Jon Harbaugh, Mike Tomlin, or Pete won't win another playoff game and have a great chance of success most seasons.
Now, if you had the conviction that Pete is the problem, you'd predict Seattle will miss the playoffs in most seasons since that's a probability only slightly skewed in your favor (56%). That's an analysis with balls attached to it. But you'll notice most people who detract from Pete don't make that prediction. Why? Because they know intuitively there is a higher chance that they are wrong.