I think a lot of coaches around the league do not have a good grasp on how the salary cap works, either. Kyle Shanahan holding on to Jimmy G and not cutting him to save $25M and go after a better/or at the very least same level, veteran QB for a much lower cost like an Andy Dalton is asinine.
In the NFL it is a rolling salary cap. Meaning the cap space that is not used can rollover to the next season. Teams do have to average 89% spending minimum over a 4 year period, so no sandbagging is allowed. But spending money for the sake of spending money is not wise. The key is to spend the money on good players, and don't waste money on bad players & JAGs. The cap space Seattle currently enjoys isn't burning a hole in their pocket in other words.
With that being said, teams currently have the ability to kick the can down the road to the tune of $1 Billion dollars (approximately) guaranteed and counting (As the cap goes up.) Plus teams can tack on voidable years at any point to lower a player's cap number, or restructure if they want to keep the player long term while still lowering their number in the short term.
The salary cap is secondary to teams, and the bottom line ie: profits being the #1 priority, is the much greater inhibitor to teams spending money and acquiring players. Like any well run business they have a budget. The salary cap was created by the owners to keep player salaries down under the guise of competitive balance. Same with the rookie wage scale, although I do agree with the owners on that one, top drafted rookies coming into the league having never played a professional snap shouldn't be some of the highest paid at their positions like it was back in the day.
There is way too much hand wringing on the subject. The salary cap is easy to manipulate and teams (including the Seahawks) do it all the time.