I used to think that. I've recanted. I'm still not 100% sure why leaders are so important, but the evidence I've personally seen over the years is pretty clear.
My best guesses are some combination of:
1. It is true that the performance of a team is given an upper bound by both the quality of the team and the quality of the leadership, but people tend to badly underestimate how much quality and talent there is in the world. The average person is above average in some significant way. I would agree world-class results require a world-class team, but I think in general, for a given "random"  selection of team and task, it's a rare time when the core problem is a true lack of talent. Don't get me wrong, I'm sure it happens, but I've never personally witnessed it in 15 years. Whereas, I've personally witnessed many teams failing to live up to their obvious potential because of bad leadership. So, in a sort of mathematical sense it is true that neither leadership nor team talent is more important, in practice, leadership is the thing for which demand is much higher than supply, not team talent.
2. It is true the team is who provides the day-to-day progress on a problem, but it's generally the leadership making a lot of little decisions that add up over time; little words that affect morale, small key decisions that affect efficiency by a few percent, that little bit of vision-from-experience that avoids blowing a few days on a bad path, the careful selection of problems to personally take on. It adds up to a lot, and especially when the leadership is blowing these little calls consistently, no team is good enough to undo the damage... especially when the leadership actively prevents it!
I do agree that it's important not to fetishize leadership and never to forget the team gets much credit too, but over the years my estimation of the importance of true leadership has been going consistently up, not down.
: By "random" I don't literally mean five people uniformly randomly chosen from everybody on planet Earth, but something more like, go out to a random company and get a random team working on some problem, and it is unlikely that the most pressing problem the team has is a raw lack of talent to complete the assigned task. Again, totally non-zero of course.
I'm not sure I buy that. I don't have strong evidence against it, but its a gut based on experience. What I've tended to see is that great leaders tend not to be able to replicate their success. But talented people/teams tend to be succesfull, regardless of the leader.
To put it another way, a great leader, moved to a new team often is not a success. In fact, when they are, it is usually somewhat unusual. A great talent moved to a new team is rarely not a success. And when they aren't is somewhat unusual.
And what I've found is that the great leaders who can replicate success are those with huge personalities that draw in great talent. Or their reputation from their first success gives them considerable leverage to use in new ventures.
For example, look at pro basketball coaches. Getting a great head coach almost never drastically changes the record of a team the following year or years, more than chance would. But getting a great player almost always increases a team's record. What a great coach does though is bring in top talent -- but usually slowly, given it has to be done via free agency.
Jobs could go anywhere and get top talent. His ability to lead is also his ability to recruit. I'm not saying he doesn't bring other things to the table, but I'd say that a good percentage of it is recruiting.
Let me put it another way... given two choices, what would you take:
1) Steve Jobs's mind transplanted to some average mid-level manager at HP. No one know him as Jobs, but he would have Jobs's managerial chops.
2) Steve Jobs body and name, but his mind replaced with some mid-level manager at Apple (who of course is aware of the fact that he needs to keep up the charade of being Jobs).
There's a reason why entreprenuers who are successful, but when they leave their domain (go into a completely new field) are no more successful in future endeavors than anyone else. The second hit borrows greatly from the fact that people recognize you have already hit it out the park once.
I'm inclined to agree with you, but the problem with that claim is that it is practically unfalsifiable. Nobody has or is going to try an experiment where they put someone like Jobs elsewhere and deliberately constrain his recruitment access only to average or slightly mediocre people. So, we can assume it's because dynamic, powerful leaders attract good talent, but I don't think there's a solid empirical basis for that without consistently studying what happens when they are specifically denied good talent.
I've worked with some great teams, but if there's not clear leadership (and specifically, good communication) things fall apart. I understand that certain decisions need to be made by the founders, but when there is no good communication and they are pivoting like an elementary school basketball player, it doesn't turn out well.