If I were brand new and wanted hand-holding, I would use a TA that was totally available to talk to me, that had traveled, that really knew what they were talking about. Frankly, I'm not sure I've ever been that new, LOL...
So I use a TA if I get something from it. A good onboard credit, cash back, etc etc. I don't need hand-holding. I've found that with both Royal and Disney I can call in and do a variety of things, as long as I tell them WHAT I want to do before telling them my reservation number. That way they know what I'm asking about, and they don't stop me with the "you booked with a TA" bit. So it's requesting distilled water for a CPAP, requesting an extension cord, once I even changed the spelling of DH's name when the phone call with the TA had resulted in a misspelling...that sort of thing.
You have to go through the TA to change rooms, add people, subtract people...the things that will change the costs of the cruise.
Having a TA limits you, but not 100%.