yes, that's very true and I think it's important to point that out to people who ask, it's not an impossible thing, because, obviously some people achieved that goal. BUT it's a question of investment.
John Carmack has incredible skill and spent every bit of his time to make things happen, while his friends made the business side == 50% skill, 50% time, 1% money
bill gates created Microsoft/dos: he bought from another company DOS while making a deal with IBM: 50% skill, 1% time, 50% money
I wont make an example for 1% skill, as that might sound a bit offensive and judging. (and it doesn't mean someone has 0% skill, it just means 1% of the investment for the success of something particular is skill)
if time == 0, but infinite skill and money, obviously you won't get it done, 0 days of investment is not enough. even if you'd consider to hire a person to do all the work for you, you'll need some time to find that perfect person
if skill == 0 but infinite time and money, you won't create it yourself, you also won't be able to hire anyone who can do it as you cannot judge other skills without having at least a bit of them (it's like trying to find the prettiest girl friend while being blind).
if money == 0, but infinite time and skill, you won't be able to buy food for the time, buying equipment or marketing.
but on the positive side, if you have infinite time (because you're unemployed) or infinite skill (because you're genius) or infinite money and a little bit of the other skills, there is a good chance you could make it.