From a dive guide's perspective, 99.7% of the people we dive with fall under the category of inexperienced "instabuddies", and I (usually) very much enjoy diving with them. For most new divers, having someone spell out the basic parameters of the dive (entry, general underwater plan, depth, time, air, signals, exit, special considerations, etc.) is enough to put most of their anxiety to rest if the dive is within their skill level to complete.
Realistically it is sometimes impractical to have the new diver (instabuddy) completely plan the dive, especially if this is their first time diving the site or area. That doesn't necessarily mean they aren't ready to do the dive though... If every (now) "experienced" diver had only ever done the same type of dive over and over and over when they were starting out, they would probably still be missing some crucial dive skills and experience.
For example, we get new groups of divers every 1-4 months that are going to be collecting scientific data underwater. 99.9% of these divers have just completed their OW or AOW class and have exactly 4 or 9 dives respectively in conditions that were extremely different from where they are now. It would be unrealistic to have them plan the specifics of their first few dives here since they don't know the sites, entry/exit protocols, or environmental factors. However, it is not unrealistic to have them come up with some aspects of the plan like depth and gas management. Having them think about why it is important to turn at a certain point, or keep a certain amount of air in reserve is only going to help them learn more as a diver.
Once we have [-]beaten their bad habits out of them[/-] made sure they are comfortable and competent underwater, we usually then have them plan the entire dive. After the initial shock wears off (since many have never "led" a dive before), they usually realize that even if they aren't intimately familiar with the site, they can figure out a plan based on what they know from previous dives.
Details like exactly which direction they will turn at the bottom of the mooring are less important than understanding the reasoning behind things like staying on the wreck or taking a compass heading, staying close to your buddy, or swimming into the current.
The same idea works equally as well for an "instabuddy" you might only be diving with for a day. It's not bad for the more experienced diver to be the one truly leading and/or planning the dive, but everyone has to understand why the plan is what it is. I think that way even if someone forgets a minor detail, they know the underlying reasoning behind that detail and can usually deduce what their next step should be.