In any case in my opinion crisis core did flesh out a lot of the story, like the war with wutai, the origins of sephiroth, who the **** zack was, the relationship that zack had with aerith, aerith's youth and relationship with tseng etc etc, those where missing in FFVII, if you did the subquest to find out who zack was in FFVII all you got out of it was that he was a soldier, that got gunned down for carrying cloud around, as to the why and how it happened and how did it get to that point, nothing is mentioned in FFVII.
All of this is covered in VII. The only thing it shed light on was Zack's character development. The rest we already knew about and I didn't need to have covered in another game. Angeal & Genesis both are as "WTF" as the entire plot of Dirge.
If you're going to add on to something - I'm going to paraphrase you because it's how I feel - you flesh out the world by adding a lot more "ahh that all makes sense now" rather than add more "WTH is going on here." That's what I mean by our definitions probably differ. Crisis Core didn't add anything (other than insight into Zack as a character - cause all the other characters were basically shells that he interacted with as far as I recall) that I didn't already know or think was covered other than nonsense about additional Nomura characters.
I also disagree with your assessment that the story was not complex or engaging (you knew I would) but I probably won't change any minds by getting into it - unless someone specifically cares that much about my take. I would say "engaging" is really personal preference, but it is easy to defend the "complexity" compared to other games at the time (and prior to it). I honestly can't think of a rival in complexity at that time other than Xenogears - which is also complex to the point of confusing at times (like understanding Cloud/Zack relationship and Seph/Jenova relationship). I guess "convolution" and "complex" are possibly a fine line but I think (as far as JRPG go) FFVII is not the typical "Oh no! World is in danger! Round up the cat/bunny girls and lets get cracking!" It's got a lot more under the surface.
Feel free to disagree with me on that. Many do and that is actually one subject I do get tired of talking about because it usually digresses into the post I'm about to quote.
Please stop talking about FFVII, I'm trying to read up on the state of FFXIV and all i hear are people discussing old tired topics
This is an intelligent discussion about the merits (or lack of) a related game which given the contempt (and evidenced by your comment) are far and few between. As long as someone is interested in my opinion (or sharing theirs) on the subject of VII - I will not desist.