2004 technology aside, this is called the "Good Enough Factor". Obviously every super geek at NASA wants an 20 MP camera with full zoom,100 year lifetime, 3d, blah blah blah. But, they are working in very exact specifications and budget. So, you have to opt for the option that satisfies the Good Enough Factor.
What will get us closest to what we actually want, without totally breaking spec and screwing with the time and monetary budget.
Everyone is missing the point here. The problem isn't that these cameras are old tech and using outdated CCD censors. If these were the best images we've seen to date of Mars, you're right, there'd be a "Good Enough Factor" — the best images we've seen from a NASA mission, but not as good as modern DSLRs. Understandable.
You are comparing the very first initial images from Curiosity with the final processed images from Viking. Also, the haz-cams on Curiosity are there only to help Curiosity see where it is going. Whatever design trade-offs they make, they need to make the priority be "don't break the 2.5 billion dollar rover that is supposed to last for over a decade."
If you use a low-res camera to take 1000 images of the same thing, you can use software to make a high-res image from those.
What will get us closest to what we actually want, without totally breaking spec and screwing with the time and monetary budget.