There is ignorance and/or complete ignorance at many big box gun stores and there is a real difference. Ignorance is very common when the store employee either does not know what he is doing or is misinformed about what he thinks the facts are or is just flat out mistaken. Might just be a simple lack of knowledge, and to be fair who know about all the rifles, pistols and shotguns out there and what their fair market value might be.
Complete ignorance is another matter. Then the person is pretending to know what they are doing, often with a desire to sound like they know what they are doing when they really do not. BS artist is another way to look at them.
Most big box gun room employees have very limited real knowledge. If you have more than one real smart fellow in the gun room it is a very well staffed room . Most have about a half smart person and a smart buyer suffers. It is hard to work with any expert when you know more than the expert does. You have to teach them what they do not know to get them to do what you hope they can or will do for you. Most of us just give up and go elsewhere.