I think it's probably pretty easy to agree on what a skilled diver is. Effortless buoyancy control, the ability to control one's impact on the dive site to the degree one wishes to control it, wide-ranging and acute awareness of the changing dynamics of the dive, including one's buddy if there is one, and the ability to cope with malfunctions and inconveniences smoothly and calmly are all skills I think most of us would agree belong to a skilled diver. I'd add the knowledge to plan a dive adequately, including assessing hazards and having appropriate contingency plans. Those are all skills.
What makes a GOOD diver is almost certainly more of a subjective determination each of us must make. To me, being a good diver includes one's attitude, which should be humble. I personally don't consider someone a superb diver if that person is doing amazing feats of exploration but is dismissive, rude or patronizing to others who are not. I also include good judgment in my list of necessary characteristics. You can have perfect control of yourself in the water, but if it routinely puts you where you or your companions are in danger, that's not good diving -- to ME. Others may find that a desirable part of what they do.
I also include an awareness of the environment through which we swim, and an attitude of conservation. This means if you fish, you learn enough about the species you're catching to know the life cycle, and which individuals are most safely removed from the population, and you watch the areas you fish to see what's happening to species and distribution. (The open fishing side of Anacapa made a durable impression on me.)
And because I'm who I am, my opinion of someone as a diver skyrockets if that person has indulged his curiosity to learn more about what lies behind what we do. I respect people who have learned about equipment design and manufacture and repair, or who have studied what's known about decompression.
But I do think the definition of "good" will vary according to how each of us ranks a whole list of qualities which do not fall under the strict definition of "skills".