You need a top 10 QB to be a contender on a year to year basis.
Otherwise, yeah, you can once in a while make a run here and there like Minny or Jags did.
As @Danny @TedSlimmJr and @foozool13 have said, it's the biggest piece, and without it sustaining competition at the level needed to compete for a Super Bowl is almost impossible. If you want to build a team that is competitive for a decade, the one irreplaceable piece is a top QB. Just the way it is in the NFL with today's ruleset.
Additionally, as a fan, there is no more enjoyable piece a franchise can get than a good QB. Win or lose, not scoring points isn't fun. I enjoy defensive battles, don't get me wrong, and I can get into a dominant defense. But literally every team is more enjoyable to watch with a good QB. As a fan, I'll watch the game even if we're eliminated … and if we're going to lose, I'd rather lose 40-35 than 6-3.
And the dropoff from QB value to the value of any other position is like falling off a cliff. Even the bad QB's are going to cost a lot, so there is no better bang for the buck than to get a good QB. Get one on his rookie contract, and it's a downright steal.
Do we need a top shelf QB to be Super Bowl competitive for a decade? Yes.
Is the QB the most important position on the field by far? Yes.
Will settling for a mediocre QB set back a franchise for at least half a decade? Yes.
I don't think any of this is really being debated even … we all know it is true deep down inside. The only question is HOW to obtain that QB. Some think our current strategy of competing hard and drafting QB's outside of the top of the draft will yield good results, after all, the extremely rare exceptions like Brady (mid round) and Marino (late first) and the recent short mobile QB's like Wilson suggest that people have found QB's outside of the top of the 1st. But that theory ignores the literally hundreds of failures as well. The real statistic would be the hit-rate … percentage of elite QB's found with picks throughout the draft. It's complex, but the data indicates that your chances of finding that elite QB go up dramatically at the top of the 1st round. To get that draft pick you can either tank or mortgage the future with multiple firsts. Differing viewpoints abound … and everyone has an opinion.
Personally, I know what I want. I want an elite QB who can throw the ball exceptionally well. If it were possible to get another Dan Marino, that would be my solitary goal. Alas, he is unique, truly one of a kind. So, I'm seeking an elite QB, and I'm willing to mortgage the present (2019 season) to get it, so I can preserve the future (additional draft picks needed to trade up to get him if we don't tank). Reasonable minds may differ on how to obtain a QB.