Med- good point, we've ALL been that guy when we first started boating.
Speak for yourself!
Seriously - I'm a advanced windsurfer, sea kayaker and had crewed on several boats before I bought mine. I work in commercial construction, so I have a lot of respect for weight.
While I was confident about sailing the boat at sea, I was a big weenie when it came to operating under power in confined areas. I knew about (and respected) tides, wind and weight.
I utilized the crew list I used to get rides, in reverse, saying: "If you want to sail on my boat, you must have experience skippering".
Often, I sat on the boat at the dock, itching to be sailing, but afraid of taking her out of the harbor by myself!
It retrospect, I laugh, as I was being overly cautious (aka...PARANOIND).
On the other hand....I was never "that guy".
Of course, most take the more conventional route of sailing school. From what I've seen, more emphasis is put on sailing, than motoring several tons of vessel with 5 feet (plus) of keel and a 40 foot (plus) vertical stick attached! Perhaps creating "that guy".