By that I mean the kind of business instincts that are needed to really make a killing in the marketplace.
There seems to be an abundance of admirable nobility in the aims of YCers but not a lot of ruthlessness.
Maybe this is a function of the relative youth and inexperience of most of the groups that apply.
Would YC be more profitable if they were more open to older entrepreneurs that are ready to rumble?
Let's start by clarifying your question. Did Larry & Sergey, when they started, have these business instincts about making a killing in the marketplace that you're referring to? Because if they did they seem to have been well hidden. And if they didn't, these qualities don't seem to be worth much.
Also, can you tell me more about the youth and inexperience of the people who apply to YC? No one, as far as we know, sees the applications except us.
Your last question I can at least answer with certainty: no. It takes 4-5 years for a startup to achieve liquidity. No YC-funded startup is that old; the median is only about 18 months old. Our profitability now is therefore noise, which means no change in the applicants would have affected it significantly.