First off there needs to be a line drawn between punk music and "Punk Music". There is the genre called "punk" which was completely ****ed sideways by people like Greenday and other ****ty rock bands who played loud and fast but were not really ever punk bands.
Punk still exists though, you can find it but it won't really find you usually. It like all punk music it isn't ever played on the radio. Mostly because it is almost always offensive. Old punk is never even played on the radio. I've never heard black flag on the radio.
If you want really cool newer punk bands then I would suggest The Fatal Flying Guilloteens, Die Princess Die, or the Locust. Charles Bronson (the Band) are also pretty good. You could call the Mars Volta punk, but mainly their first album "Deloused in the Comatorium".
The point is there is a major difference between "old punk" and "new punk". Punk is a philosophy and intent that directs people and their music, it is not a genre. The original punk bands where not connected by a sound they were connected by the way they lived and their attitudes.