This is the major thing. The bad ones don't do any homeworks and basically just spam based on keywords. The good ones at the least look at my profile/resume and

This is the major thing. The bad ones don't do any homeworks and basically just spam based on keywords. The good ones at the least look at my profile/resume and can articulate why I would be a good fit for position X based on my history. I'm always polite but some of these people clearly have no idea about the positions they are recruiting for, especially the differences in technology. Then you have the pushy ones. "How much are you making now? Well this position pays 20% less I want to submit you for it", no thanks.