Too many teams fall into the trap of assuming they are guaranteed something by not "mortgaging the future" which makes absolutely no sense. Lot of GM's around the league play it too safe when the franchise hasn't won anything in many years or at all.
What the Rams did going all in for Stafford, Ramsey and others was the right move as they haven't won a Super Bowl since 1999.
On the other hand, you have the 49ers making the massive mistake staying with the younger Jimmy G than signing a guaranteed All Pro QB in Tom Brady who would've also brought his posse of Gronk, AB and attracted some lower tier FA's. They've would've won at least 2 Super Bowls by now. But they are currently struggling to keep any window they have left open.
I have no idea why the Bills haven't made major moves while KC's team continues to get weaker. Now they are on the brink of getting surpassed by the Patriots who are going to continue to make moves with the amount of cap space they have.