Refereeing a lazy, but correct paper When refereeing a paper, I often have objections to the work that do not rise to the level of using the coercive powers of a referee to delay or reject the work. For instance, I find myself wanting to write: "If I were you, I would be embarrassed to publish a paper with [such unclear writing/such a silly comparison to experiment/so few parameters studied/incredibly ugly figures]."*

If the paper is not wrong or incoherent, just lazy or badly written, I don't feel justified in rejecting the paper or requiring a revision. I also don't want to invest hours of time acting as a language editor or graphic designer for figures. 

Is there a politer way to express this sentiment and encourage the authors to improve their own work? Or should I simply take on good faith that the authors have done the work to the standards they are willing to publish, and that these may differ from my own?

*note: this is distinct from the case where the paper is so unclear that you can't tell whether their work is correct or not - where I think rejection is appropriate. I'm also assuming that this is not a terribly selective journal - in fact, it could be a journal like PLOS ONE, which explicitly says that importance to the field is not a relevant criterion. 

Note: I've edited this to address a couple of points made by answers, and to focus away from the writing part, which has been answered in the past. Bad writing is one aspect of this question, but general author laziness is the larger one.
I think there are two important factors here:


Reviewers are typically the closest subject experts a journal can locate. 
Most journals have (or want) a target audience that is considerably broader than the expert reviewers they enlist. Think of the industrial practitioners, novice grad students, and other interested non-experts. 


If it takes you a lot of effort to parse and understand a paper as the related expert, it seems entirely plausible that a non-expert would not follow the paper at all. Particularly if the poor exposition is so bad that you can only follow the train of thought because you as an expert can fix errors in your head or make logical leaps, then it's definitely beyond the scope of the general reader.
Both are valid complaints that could lead to a rejection of a paper, depending on the particulars of the work and the venue.

There are other avenues to address these problems than simply rejecting the paper. If the work otherwise is adequate, you might say so but tell the editor that the work does not meet the language standard for this journal and let them handle it. Some journals have a notion of "conditional acceptance" or "shepherding" where an agreement is worked out between the authors and editors that certain items must be addressed or revised prior to publication (however, they need someone to oversee such papers, so you might be volunteering for the role if you suggest it!).

Nobody wants a rejection, but most authors do want their work to be read and appreciated by others. Addressing these issues is a short term frustration for authors but a long-term win in terms of the visibility and impact of their work.