If for whatever reason, our entire population was able to go to College/University and graduate while successfully completing the required curriculum then they would be higher skilled and would probably earn more.

I mean, we're pretty much there now. The OECD doesn't call us the most educated nation on earth for nothing. Despite being the most educated nation, we're not the most well paid nation. Not even close. Canada only ranks 11th for highest average wage in the world, again according to the OECD. And the gap between us and the top is fairly large. If what you say is true, why are we not actually earning more than many countries that have far less schooling than we do?

What even gives you the impression that they would earn more? Price is ultimately determined by what someone is willing to pay. Are you going to pay more for your lettuce because the grocery stock boy has a degree? Are you going to pay more for your Big Mac because the cashier at McDonalds has a degree? Why would you? The product hasn't changed. You're not getting any more value just because the people involved spent more time in school. Where is the extra money going to come from?

In fact, in reality, if everyone was in that position, high paying jobs would start to decline in price. As price is a function of supply and demand, the increased supply would result in lower wages. You can even observe this in the real world if you look to certain careers. Software development comes to mind as a notable example to r/canada. While perhaps still relatively high paying compared to other careers, Canadians are paid a fraction of what American software developers are paid because we have so many more people willing and able to do software development. If all Canadians were willing and able to do softer development, it would be a minimum wage job.

I'm not saying that having a piece of paper automatically earns someone more money, but rather the process students go through to earn those pieces of paper make them more employable and that opens the doors to higher paid professions.

But in reality you just get the top people taking the top jobs and the average people getting average jobs and the bottom people getting the bottom jobs. This is why incomes haven't changed with increasing attainment. Getting that piece of paper doesn't change the market. The market doesn't stop wanting McDonalds hamburgers because you got a degree in astronomy. Walmart isn't going to open a space observatory because you got a degree in astronomy. It doesn't work like that.

High income earners are disproportionately University or College graduates.

Absolutely. And even if we assume, for argument's sake, that it is a perfect gradient where each increase in level of schooling leads to being in a higher percentile income-wise, what you are ignoring is that the large majority of the population have that schooling. Most of them are not in top income groups just by the fact that they mathematically cannot be. So again, you're ignoring the majority for the sake of the outliers.