The NFL has an interesting situation right now.
The conventional wisdom used to be that in order to be successful or even competitive, you have to have a great QB.
This has led to teams essentially repeatedly driving themselves into the ground in order to get a bad enough record that they can get a good enough draft pick to get the QB. But since QB drafts are not an exact science, you are left with teams repeatedly having to go back to the well to get a QB.
This has led to a frenzy for QBs though, and that means keeping a QB so much more expensive it strips the team. So now, for the most part (Patriots not withstanding), having a great QB means you will be competitive but likely not successful.
The key to the SB no longer is getting the great QB and riding a mini dynasty for a few years. Instead it is getting a rookie QB, finding other high impact 1st contract players and then filling the gaps with all pro free agents.
The teams with good to great QBs still have good records to keep the fans engaged. The teams with bad records that draft a good or great QB can suddenly end up contenders in year 2 or 3 after that draft just by leveraging the increased budget available because the rookie QB salary gives them so much more spend than teams with veteran QBs.
It all works out perfectly for the NFL to keep teams competitive, which is one of the secrets to their success.
(The problem is that the mid-tier and lower tier QBs are getting huge contracts and so you get teams like Miami that get stuck with whatshisname, who they cannot even trade. Or the poor Jaguars after their godawful extension of Bortles.)
So the key here is that extending Wilson means we won't be reaching SBs but it means we will be reaching 9-11 win seasons regularly. That is how the system is set up. Teams with great QBs will have strong regular seasons but will always have glaring weaknesses that will usually cause them to fall short in the playoffs.
Wilson knows, we are a team with a lot of our better players on 2nd+ contracts. Even with his GIANT contact, if he goes to a team with a lot of young players on 1st contracts - he can probably still contend. He will not be a contender here, and worse, he won't even put up numbers that would get him the production he needs to leverage for the kind of legacy he wants to leave. 200 yds per game won't cut it, it isn't his fault but it might be his record unless he leaves.
Important to consider the earlier paragraphs, staying here he isn't getting to the Super Bowl. Somewhere else he has a small chance, but that is better than almost zero in our current situation. I see Wilson pushing to go to a place with a lot of young impact players where Wilson's impact to the salary cap will not hurt their chances as much. I don't see how the Giants fit this mold though.