Slashdot's content is entirely created by its users. If Slashdot sucks, then, whose fault is that? It is entirely within the power of you, the disgruntled Slashdotter, to improve its quality. Submit an interesting story. Post a clueful, well-reasoned, and factually correct comment. Meta-moderate. You have many options for making Slashdot suck less: so instead of standing about whingeing, contribute!
Or, as an alternative, leave and do something else. Take up a nice hobby like macrame. Read some other web site. Start one of your own. No one is forcing you to read Slashdot. The people who choose to do so probably do it because they find some value there, and don't find your cries of "Slashdot sucks!" to be helpful or interesting. Help make it better, or leave.
A common complaint among those who think that Slashdot sucks is that the Slashdot moderators are all on 3 dollar crack. The assumption that Slashdot moderators are a bloc that pursues a common agenda is bogus. Any Slashdot user with positive karma (a status trivially easy to maintain) gets the opportunity to moderate. This means that at any one time, liberals, conservatives, right wing maniacs, Linux lovers, and Microsoft employees are all going to be moderating. Any percieved agenda or bias over multiple moderations is nothing more than statistical accident; moderators do not coordinate with one another. Over time, the biases of the individual moderators even out and quality posts rise to the top. And, yes, this includes posts that are critical of Linux, Open Source, and other ideas often claimed to be Slashdot sacred cows.