The part I was referring to is the bit about "meaningless existence".

That was the whole FOUNDATION of FF7 and it would fit straight into Sephiroth's dialogue - in fact it may even be in there. He's always reiterating that cloud is a puppet, meaningless etc. and his efforts are futile.

In FFX it didn't seem to fit because they hadn't really expanded on the idea of their lives being meaningless.

That's just how I interpret it anyway.