In addition to indubitablysnarky's points consider the following:
1.  His level of play 5 years ago is not the point.  In San Francisco his level of play moved him into a backup player role.
2.  For the other 31 teams he would have a long learning curve as he learns a new offense before taking the field as its most important cog on offense.  
3.  He turns 30 next month meaning that a typical career would be 1/2 over.  This diminishes the time his learning could be amortized over could only be 3 or 4 years.
   
and NFL Team owners still hold their 5th Amendment Property Rights enabling them to not have their property taken from them.  Something that a polarizing player would do by antagonizing part of the fan base.  To ignore this reality smacks of incredible naivety in reviewing this story.