In a way I have to agree with you about many travel agents. If there is one thing I have NO tolerance for it is a professional anyone who says they are experts in a given field and I find out they have no real experience at all. They are often called "paper-experts" because they may have passed a class, but they aren't well-informed.
If you meet a travel agent who wants to sell you a cruise and they don't even think to ask you basic quesrtions like "do you belong to any loyalty programs" or "what kind of stateroom do you want," then you need to find a cruise professional.
There are certain cruise agents who truly are assets. But they are rare.
In general, I want a BUSY cruise agent, because that tells me they do enough volume that they don't have any time to do anyting except take care of me. A cruise agent that has spare time is probably trying to figure out how to get a higher commission out of you.
A busy cruise agent will just do as you ask and get it done because they have a dozen other things to do. And they won't mind if you ask for a credit due to a best price guarantee because they are more interested in building out their stable of customers than they are in getting the most out of the few customers they have.