When news of Patrick Mahomes' contract extension first broke, it was notable for two reasons. The unprecedented dollar amount—$450 million in base value—immediately jumped out, but it also meant that the Kansas City Chiefs won't have to worry about losing Mahomes until 2032 at the earliest.
Trying to replace arguably the best quarterback in the game today would be a nightmare, and teams face similar challenges yearly.
No, not every franchise has a Mahomes on its roster. However, each team has players who, due to talent, upside and/or scheme fit would be tough to replace through free agency, via the draft or in-house.