hersheybear you are not the only one so don't kick yourself for not realizing this. I was here for more than a month with really horrible losing teams. I assumed that the AAA were thrown in as a sort of gimmick - giving owners someone to trade for the fun of it, or whatever. When I realized that these were real players and often good ones, I felt exactly as you do now.
I suspect this is a common, almost universal experience on the SIM. A friend here at about this point in my experience told me there is a learning curve and to be patient as you learn to build winning teams. I haven't won a championship, though I have had a number of teams make it to the LCS and more in the playoffs and one lose a World Series. So you get there.
No better advice can be given than to read the forums. See also elbirdo and contrarian23's posts about pitching and about understanding fatigue. Just for starters.