Classic prog vs modern prog

High-five! 

No, Can was awesome during that time period... Arguably their best three albums were released in 1971, 1972, and 1973. I cannot recommend Future Days enough for any prog fan!

I think maybe one of the things the OP was getting at is that there are modern bands who have the classic rock sound and ones that don't. For example, The Flower Kings(if we can call them modern)and Transatlantic do have that classic sound but bands like Porcupine Tree(well the later stuff anyway)and the Mars Volta do not. My guess would be most of the "crossover" prog bands have a more modern sound as well. 

Here's my take on it. The classic bands from the seventies were obviously influenced by classical, jazz, folk, etc and not so much other bands at the time since there weren't a lot of bands that were trying doing prog in the early days or stuff that they were influenced by. Of course there were some exceptions like the Beatles and King Crimson who influenced a lot of later prog bands and a few others like the Moody Blues, the Nice etc. However, mostly the first wave prog bands were just throwing in everything but the kitchen sink. The modern symphonic bands were influenced by the early prog bands(Yes, Genesis, KC etc)and so it's often rather obvious which bands they were influenced by(the Flower Kings and Spock's Beard for example). With modern bands who aren't retro sounding or overtly symph prog sounding it's less obvious who their influences are as far as prog goes. Some of the more indie sounding bands could be influenced by indie rock or alternative or whatever. I can't think of any examples off the top of my head but I know they're out there.