Most football players are, in real terms, disposable. It’s no secret. Their team will sign, train, teach, and motivate them. They’ll have them out in their respective communities doing public service and help them bond with their city.
Then, they eventually let them go in favor of someone younger and cheaper who can perform similarly. The Detroit Lions are no different. Despite the element of immorality to it, this is the reality of the salary cap driven business of NFL football.
The often exception to this is the so-called franchise quarterback. These relatively few men are the team leaders that carry the weight of the fortunes of the offense, and often the entire team as a whole.