Hahah, I see what you did there.
And I kinda agree you're right.
In my opinion, it's because of the new generation surpassing the old one excuse.
In reality I found it more as in some sort of maturity.
And why do I say this? Because of an interview I read from Kishi where he says he needs to write about Sakura needing to grow to surpass Tsunade, something like this. And it was more referring at the maturing state, because to be honest, I don't even see Sakura surpassing Tsunade in endurance, at least not now. I see it as to mature from her experience and something like this (sorry for the parallel, might not be to everyone's taste).
The same matter with Sasuke and Naruto.
They not only have grown powerful, this was going to happen, since they are the main heroes, but in my opinion, it's more about getting mature, as I said before.
Nice thread.