Why do people measure the congress' success by the sheer quantity of bills they pass?

Because it's what they do.

Your premise is false. Quantity is not the only measure. The problem with the current congress is even routine bills passed every year by Congress is not getting done. For example Congress every year passes a Defense Policy Bill which establishes the Congressional approved defense policy for the nation. This is a routine bill passed by every Congress for decades. But this Congress can't get one passed.

It is not just quantity or quality, but routine items that should be passed.

I guess to someone who isn't really paying attention; quantity means something, because at least they are doing SOMETHING rather than getting paid to do nothing at all.

In the long run of course, quantity means nothing, and while quality should mean a lot it doesn't. I'm of the belief that there can't ever really be a quality bill because everyone disagrees about everything and everyone is only in it for themselves. Something that appears to be good is usually drowned in so much legalspeak no one can tell up from down.

1) Lack of intelligence.

2) Not for that crowd.

Not to Demacrats

Your premise is false. They don't.

That has been missing also.