Actually, I have yet to have a single Grell, Mind Flayer, or Beholder appear in my campaign. I could see myself using Beholders, as I don't have anything against them, but I haven't had a need for them.
My campaigns tend to be very humanoid-heavy. I like providing mostly intelligent adversaries for my players' characters. Also, given the type of characters and their personal motivations, it just makes more sense for them. That's not to say that I am opposed to having them encounter the occasional mindless terror, but due to the nature of the campaign, which has two separate but converging underlying themes, both rather humanoid-centric, they are generally unnecessary. Of those mindless terrors, a good percentage are of my own design.
I also tend to keep a fair number of unique, or exceptionally rare, monsters in my world. For instance, there is a certain mountain pass near the southern part of the continent that is home to about a dozen apparitions (ghost-like, but with different stats/powers) due to a bloody ambush that took place there years ago. The characters have never had the misfortune of meeting any of these spirits, as they are too terrified to attempt to traverse the pass when there is a chance of not making it through before sunset. Of course, I plan to engineer a situation where they will have to make a tough choice, namely risk the pass or face a known danger, but I digress.
Basically, I am aiming for a particular atmosphere that I find the types of creatures found in CC & CC2 don't fit into for me. My campaign takes place in sort of a dark world, with more covert than overt terrors. I favor the creepy feelings and fear of the unknown over the in-your-face, Friday the 13th style of horror. I like to use baby-snatching cultists, rather than Bloody Flesh-eating Terrorbeasts from the Netherworld. I like to use ancient curses causing a town's water supply to go bad, rather than an ever-bleeding god at the bottom of the sea turning all of the fish into brain-sucking demon sharks.
Also, I take exception to your use of the word "argument" in this situation. What part of "I don't like the book because the creatures don't fit my campaign" is an argument? I'm simply stating why I don't use Scarred Lands materials. I'm not trying to convince you, or anyone else, to stop using Scarred Lands materials. I think it's great that you've found a setting that you enjoy. I'm not trying to convince anyone of anything, actually. I'm just fielding the questions and attempting to clarify my answers.