So because something is hidden then I am not supposed to use it since it makes the game too easy? Sorry, but if I go through the work of breeding a gold Chocobo, then I am going to use the treasures I get from doing it.

I don't think you read that properly. If I'm wrong, I apologize.

Most people won't get KOR/Omnislash/even know how to obtain these things playing the game normally. So, playing the game normally, the final boss is indeed, adequately challenging. Of course if you pimp out your characters with the best skills/Limits, then of course, anything isn't a challenge.
The only bad thing about KotR is that it's summon sequence can be a minor inconvenience. I usually just watch TV while it's going on. If I am feeling really impatient or something, then I will just Mime some Limits.
Yeah, Counter/Mime is ftw.