Husker Du were definitely very much more "protest-y" or angsty than political. You can't call "Turn Off the News" a truly political song, right? But that's probably as political as they were. I see you making the same point about Minor Threat in your next message, and I agree. However, Ian MacKaye is obviously very political figure outside of realm of his recorded music and straight edge remains a reference point for most of the modern punk. I'm not too familiar with DRI outside of their crossover trash albums, so I can't really comment on them.
I disagree with Minutemen's lyrics being generically leftist. For one thing, at least in America, you can't really reply the term "generic" to any leftist doctrine. The left in the US, from my point of view, is really amazingly divided. Bernie Sanders and Beto O'Rourke are pro-Israel, for instance, while most of the leftist part of their electorate is definitely pro-Palestine. There are various more differences and disagreements in economic questions, too. The leading Amercian leftist publication of today (Jacobin) is very anti-Maduro and constantly publishes pieces on how economic policty in Venezuela is a huge mistake, while the leading leftist voice of the American kids (Chapo Trap House podcast) completely disagree with that. There are practically no uniform leftist positions outside of common slogans. But D. Boon's lyrics definitely do go deeper than those slogans and do not scratch the surface. He advocated for a lot of things that would be considered too radical by most of the American leftists nowadays. Granted, he did write songs like "Shit From a Old Notebook which are nothing more than slogans, but at the same time he was sort of a pro-armed revolutionary, which is a philosophy that is definitely not that welcomed in the mainstream American leftist circles.
Dead Kennedys is another story altogether. Remember someone's quote about how Bob Dylan was a journalist and not a singer? Jello is 5X times that. He is even more radical in his views than D. Boon, but most of his lyrics are tied to the actual events that are very difficult to decipher if you don't know the history of the early 80's.
Music is definitely not enough for the kids those days, IMO. But then it doesn't mean that the bands I've mentioned are actually bad at it. Downtown Boys are fantastic, IMO, and you should definitely check them out, especially if you're a Minutemen fan.