Absolutely correct... people are wasting their time in getting links from low quality sites as they think quantity of links dominates quality.
Don't simplify too much, imagine that position of your site calculates by following abstract formula: Pos = X*Quantity + Y*Quality + ... (another factors) Yes, Y co-efficient is much bigger than X, but it doesn't mean that X doesn't exist
X always exists, but the main point is the value of x is much lesser than the value of y and the efforts you take out to create multiple links over low quality websites is greater than the time you might take to create a link over much relevant website. so it is better to focus on quality than quantity despite the fact that quantity does also help.
I am not saying that x doesn't exist. But we all know that Google is paying more importance to quality over quantity It is vital that you concentrate on quality links while executing your link building campaign. Correct me if I am wrong.