Why aol sux America Online is the largest Internet provider in the world, but it didn't become one without a fight. Originally a closed-in, proprietary online service, it was pried open by the public's fascination with the global network. For all of the company's past glory, it is now little more than a big communications company. America Online wants to be more than a communications company, though -- it wants to be an entertainment network, like "the MTV of the Internet." And that is where its problems set in. AOL, in a desperate bid to get subscribers in order to make itself more attractive to advertisers, went to a flat-rate plan this year, making AOL competitive on price but