I think you're onto something in labeling the Clash as "easily identifiable". They're the favorite punk band of so many because they branched out beyond punk, and have a much broader appeal. Heck, most folks in the U.S. never even heard of the Clash until the release of London Calling. They certainly didn't get any airplay until Train In Vain. Regardless, if you look at just their punk output (77-78), I think they're certainly one of the punk bands ever. And they were one of the few punk bands to have any sustainability (although, perhaps due to moving beyond punk).
For my tastes, I'm on the other side of the Clash fence than you. Give 'em Enough Rope is a fantastic album - perhaps their best. And I'm not going to say that Sandinista is a bad album. I have a certain level of respect for its eclecticism. Plus, many admire it, including yourself, and the band. That being said, I honestly find it almost unlistenable. George Martin said that the White Album would have been much better served as a single ablum. I think I'd have a hard time enjoying Sandinista were it cut down to an EP.