Any drafted player can do what Manning and Elway did. ANY PLAYER. If you come into the draft with a resume that allows you to negotiate, than so be it. Don’t blame Eli blame the system because it allows it!
There’s lots of players who hold out or don’t sign. The thing that makes Elway and Eli stick out is they were #1 picks, meaning the team that drafted them had months to negotiate with them and figure out these guys didn’t want to be there and drafted them anyway. Because of the modified rules the team with the first pick gets it’s really on the team to pick a player who wants to be there, they actually get the freedom to find out.
A player drafted by a team does not have to play for that team. I assume >90% of players drafted are ecstatic that they have been drafted and couldn't care less who the team was. But there have been players who have been drafted and refused to show up to Summer camp seeking a larger signing bonus. A player can ignore the team that drafted him, sit out a year, and then become a free agent. I remember outstanding players in the past who let it be known they would not play for a certain team who had a high draft pick and that team would affect a trade for draft picks with another team. On Draft Day you commonly hear about teams trading up or down to guarantee a player goes to a certain team.
I can only repeat what I have said previously, if you have a resume great enough on draft day you can attempt to dictate your own terms. It is the nature of the beast that the NFL has created.
One last thing. The players you focus on, Elway and Eli Manning certainly have proved their elite status post draft. Elway's heroics are legendary and Manning now is a 2X Super Bowl winner and a 2X Super Bowl MVP. Both have proved their worth.