I'm not going to be convinced of that because it isn't true... MLB attendance is ~75% higher than NBA attendance. Spring Training games get covered on ESPN, too. And baseball gets less per-game coverage but more total than the NBA finals when the 2 overlap. What you're describing is not an inherent preference within SportsCenter for one sport over the other. It goes both ways.
Your problem here is with the way SportsCenter is structured and what they cover, nothing to do with a "lack of interest problem." This statement:
"If you think they are somewhat on par with the games that decide a league champion, you're not going to be convinced that baseball has a lack of interest problem"
is a logical fallacy. In this case, your problem is not with SportsCenter's relative valuation of sports, but relative valuation of preseason and postseason games. You should be telling me that postseasons have a lack of interest problem. Except then you'd be too painfully aware of what an utter moron you sound like.