What do we mean when we say it today?
Today we are not focused on action as much as Macbeth is. While that's true generally (because Macbeth is a man of action), we're talking specifically about this phrase.
When we say "the be all and end all" we are referring to an extreme situation. Or the most we can put up with. We focus on the cause or essential thing, rather than the action. What do we mean by all of this?
The "be all and end all" is the best part of something. Or the most important part of something. Even the ultimate part of something. But it's never the action that will end it for us, in the way that it is for Macbeth.
The mechanics of the phrase may have changed a bit, but the effect is still the same. We use this phrase to mean the limits of something, just in the way that Macbeth does. It turns out, no matter how you get there, the end result is the same. It's the be all and end all of it.