As an unpublished novelist who has been the recipient of many polite but dismally unhelpful form rejections, I have no real reason to love literary agents, but no real reason to hate them either, or to call them lazy because they do not feel they can sell my book. It galls me a little when I see certain ones tweeting about their partying, and drinking -- how much wine or Scotch they consumed at the last writer's conference they attended. To me, this is a sign of immaturity of the worst sort. I also do not appreciate the ones who somehow feel it is their calling to diminish and demean us, and seem proud of how many rejection letters they send. However, these seem to be a small minority of all the agents out there, and they will probably be the first ones to depart as self-publishing becomes more and more a force in the industry. Unfortunately, they are very vocal and draw a lot of attention. In reading many of their blogs, I find that they do not write as well as we do. In fact, they make the same bonehead grammatical errors they criticize us for making. I find that strange, considering the credentials they tout on their web sites.
But back to the question whether agents' laziness contributes to an author's inability to be published. As someone once said, "IT'S THE ECONOMY, STUPID!" Agents are salespeople, pure and simple. Most of them work on straight commission and take a product someone else has produced (our writing) and try to sell it to a wholesaler (the publisher), who in turn tries to sell it to a retailer (Barnes & Noble, Borders, etc.), who tries to sell it to the reading public. Now, if much of the reading public's discretionary income has been lost due to job loss, layoffs, loss of retirement income and value of holdings, the public will not be in a position to buy non-essential items such as novels. Look at the economic picture in this country and just work the list backwards -- it isn't hard to see why agents prefer to represent popular and well-known authors, even ones whose writing is not that great.
Now ask yourself if you want to sell your own product? It's hard work! Self-promotion blogging, social media, and platform building sounds like a real drag to me. Granted, the publishers want us to do it anyway, agented or not. To me this is unconscionable, as I consider promotion their responsibility, not ours. They seem to want their cake and eat it too. Again, self-publishing may cut into their business to the point where they recant somewhat on this, but only time will tell.
I do think self-publishing is going to change many things in the book trade. For some of us that will mean that our critiques will come from the buying public, not agents, editors, or publishers, and the critiques will come in the form of either sales or non-sales of our work. If it is worth it to us in terms of time and dollars spent (because both will be considerable) to be judged that way and we have the guts to do it, more power to us. However, to paint literary agents as lazy because they say they cannot sell what we write is using far too broad a brush, and is patently unfair.