I have friends with major airlines that took 20 years to get a command - and even then they tend not to refer to themselves as captain.
Their employers do refer to them as 'captain' however, having promoted them from First Officer.
All these things are subjective, but IMHO the type of person who thinks they're the 'captain' of a little boat or little plane, and feels the need to buy regalia that indicates they are a captain, almost certainly wouldn't pass a command course.
So very true! During my last decade of a long professional flying career, I was appointed as a company line trainer. As such I was closely involved in the training and assessment of several colleagues who were progressing toward command and the respected courtesy title of Captain.
What some people with a PPL who adorn themselves with gold bars don't seem to realise is what it takes to earn those. After gaining a CPL/IR and MCC, those few who manage to pass the stiff psychometric assessments, CRM and aptitude tests, simulator rides and job interview, then typically spend some years gaining experience for an ATP licence. During that time many further ground school courses are attended, scores of hours are spent in simulators and the command hopeful is closely evaluated by trainers and line trainers.
For a medium-sized employer like mine, command might be reached after about 5 years. For the largest companies, it could be a 10 to 20 year wait. Even the promotion from First Officer with 2 gold bars to Senior First Officer with 3 is no mean achievement, but there will still be a long period of line training on the company routes repeatedly until the title of Captain is rightfully earned.