The phrase it sucks falls into the broad category of maledictory expressions - terms of abuse or imprecation. It may also be appropriately categorized as profanity.
As originally used, it applies the verb suck in its specific meaning of perform fellatio. In its original manifestation, the expression's sexual connotation and strong denigration made it inappropriate in all but the most grossly proletarian and sophomoric contexts.
Current usage has worn the rough edges off the phrase, however, to the point where some younger speakers will use it in general disapprobation, without thought of the phrase's original metaphor.
Adult speakers in professional or formal situations should treat the phrase with great care. Non-native speakers should exercise extreme caution, perhaps avoiding it altogether.
Before venturing into the territory of profane, maledictory metaphor, one must be keenly sensitive to the setting, occasion and audience. A blunder in this area can be supremely embarrassing - and costly.
It would, to put it mildly, suck.
Consider as a slightly witty, somewhat hackneyed euphemism, "it creates a partial vacuum."