Your two part question has three answers. Having been a pilot for most of my adult life and having taught flying for a while, I would say that anyone can learn to fly. The caveat is that, just as there are good and bad drivers, there are good and bad pilots. The'bad' pilot is usually the inexperienced one. Seems as though when one decides to make it a profession their ability increases with experience... to be expected. However moving from the typical private pilot that flies a couple of days a month to one, like myself who flew around 1,200 hours a year certainly, of necessity, improves skills.
The problem is one of economics. Advanced licenses and ratings are required before ever being considered for employment and the more flight hours one has the more employable they become.
Here in the U.S., even with the financial problems experienced by the airlines, a new hire first office (co-pilot) will make around $20,000 the first year or so but quickly advancing to, perhaps $60,000 in 5 years with a larger airline. Discount those figures by 20 to as much as 30 percent for small carriers. A 20 year captain on larger equipment, such as a DC-10 or Boeing 747 can expect to make near $225,000 per year. This is based on an hourly figure and most pilots fly around 70 to 100 yours per month. The hiring trend has finally reversed the downturns of the last 5 years, but equally, there are more small airlines than large now.
There are numerous other types of flying that one can get into... to numerous to discuss in this forum...