When teams decide that being just good enough is acceptable it seals their fate and ultimately leads down one path, irrelevancy.
The best teams in the NFL are always looking for ways to improve. As long as they can properly evaluate themselves they are able to realize whether or not an improvement is possible. If it is deemed possible, they try to make that possibility a reality. The problem is for teams that evaluate themselves and decide that they do not need to address certain areas because they are good enough. This acceptance of performance that is otherwise considered serviceable is the gateway to irrelevancy. There is no other position in the NFL that generates this reaction than the quarterback position.
The Houston Texans are going to have to trade Deshaun Watson and there are only a few teams that do not really need to consider this option. For the overwhelming majority of the league this is a clear or possibly substantial upgrade. Matthew Stafford is another quarterback who is available who should garner widespread interest. Teams that could use an upgrade at the quarterback position and find themselves in a shorter contention window should look to make a trade that will be less costly than acquiring Watson. Either way the end result is the same, an improvement at the quarterback position.
Take the San Francisco 49ers for example. There is a reason why they were linked to Tom Brady this past offseason. It is due to the fact of Brady being a huge upgrade over Jimmy Garoppolo. Sure, San Francisco can win with Garoppolo, but they are not winning because of him. Currently they are rumored to be in the running for Stafford and it is clear why. It enables them to capitalize on their short term contention window and it allows them time to find their answer for after Stafford.
That is the difference when it comes to that top tier of quarterbacks, winning because of them, not with them. Teams that decide that they are fine or good enough often end up in a full blown rebuild sooner rather than later. An example of this is the current state of the Jacksonville Jaguars. Jacksonville decided that Blake Bortles was good enough and there was no need to improve the most important position on the field. Now the core of that roster is playing elsewhere and they are shell of their former AFC Championship Game appearing selves.
What it all comes down to is realizing the true talent level of certain positions and not believing they are better off than they truly are. Plenty of teams have fallen into this trap in the past and it has led to an end of realistic contention. If a team really wants to achieve the highest goal, winning the Super Bowl, they must evaluate from within and determine whether or not they have the right guy at the quarterback position. This process, if done correctly, would lead to a lot teams realizing that they have a quarterback who plays for their franchise, but is not a franchise quarterback. Teams that fail in this process accept being good enough and eventually become irrelevant.