I'm not really saying that. I'm saying each team can afford at least one massive contract (let's say >$25 million/year) without causing themselves big salary cap issues. There is no other player currently on the Vikings roster who I foresee them giving such a contract to. The only other player who currently makes that much is Cousins and they've clearly decided to move on from him. Hunter doesn't/shouldn't make that much at least not in Minnesota. Darrisaw is not at that level. Neither is anyone else on the team.You are saying, in so many words, that this entire team needs to be rebuilt. I agree wholeheartedly.
You could start that rebuild with one extremely expensive keystone (JJ, who happens to be a WR) and build on that. If you did it that way, it would likely be slow and tedious, and during that process you'd be watching JJ's prime years passing by while he was playing for a team slowly ascending the ladder.
The other way to do it is build from scratch. Trade JJ for more draft picks. That's the route I'd take, assuming he'd have as much trade value as I think he does. You can acquire more of the cheaper young players you so desperately need.
Just my opinion, but that's the route I'd take. If JJ was a young stud QB rather than a WR, I'd see it differently.
Unless they are planning to acquire Lamar Jackson or someone else via trade, there is no salary cap reason not to give JJ an extension. Further, since they still have control of him for 2 more years, they have more flexibility in how to structure it to keep the salary cap # from getting unmanageable in any one season.