A frustrating thing is that the administration doesn't say, "we'd like to do this but we got the best we can do," instead they say "what we did was awesome." The result is that they don't even come across as advocates for the more liberal (and quite often the more popular) position.
I share this frustration. Still, every incumbent politician in history faced with an election has regaled voters with the awesomeness of their accomplishments. When Ug was running for reelection as clan chief in 50,000 BC, he bragged about discovering fire and carving some great new wheels. He didn't mention the forest he burned down or the fact that his wheel split in two after one trip to the creek. It's not really reasonable to expect anything different during election season.
Second, Atrios links to a Dave Dayen post that links to a report that says, "A new AP poll finds that Americans who think the law should have done more outnumber those who think the government should stay out of health care by 2-to-1." And the poll does say that. However, it doesn't say what "done more" means, and the actual numbers suggest that a more liberal law wouldn't have been any more popular than what we got. Here are the basic results from the AP poll: 30% favor the healthcare reform law, 40% oppose, and 30% aren't sure. Then they asked the 70% who were opposers and not surers a second question:
So 23% of that 70% thought the law didn't do enough. That's 16%. Add that to the 30% who favor the law and you get 46%.
That leaves 54% who oppose all or most of the law. So you're still at 54%-46% opposed, and this is the best case since it's possible that making the law more liberal might also have turned some of the favorers into opposers. Of course, you can argue that this is still slightly better than 40%-30% opposed, but it's a pretty iffy thing. What's more, only 39% said they agreed with the Drum/Atrios/Dayen view that our system required a "great deal" or "a lot" of change compared to what we had before healthcare reform passed. Unfortunately, there's really not much evidence that making the law more liberal would have had a big impact on public opinion one way or the other.