Lots of things exposed us to what a fal'cie is:
Fighting the Fal'cie on many occasions //This does not explain what a fal'cie is. To the contrary all fal'cie appear to look completely different, they're random monsters, no more, no less. Some fal'cie are beneficial (the one that creates nutrition for example. Of course you plan on destroying it because the characters are assholes), some want to destroy the world, it's a mish-mash of ideas that never actually explains what they are.
The nautilus festival //You visit it at Chapter 8. Thanks for wasting 40 hours of my time
Visiting a Fal'cie temple as you said (the pulse vestige as an example) //Thanks for reminding me that there's Pulse l'cie/fal'cie and Cocoon l'cie/fal'cie just to convolute things a bit
The cutscenes with barthandellus, cid raines and the electricity plant where kujata resides, taejin's tower, oerba etc //Barthandellus is a fal'cie and yet he never actually tells you what your focus is, making him an inefficient villian. Again, this is stupid. You also meet him in what, Chapter 11?
Also, it was an escape, they did discuss a little bit but they were running away dude. //And...? They couldn't talk with each other on all the other numerous occasions when they do f*ck-all?
As always, most arguments i hear against XIII is what people hear on the internet with little to no evidence. //Or they just have a different opinion.