The synthesis of art rock ambience with dancible funk music is what makes Can interesting.
There is lots of variation in the atmosphere/texture throughout the piece and not only that there is a sense of emotional journey/dramatic arc (aka spirit of sonata form) in the piece as well. As long as Halleluhwah is, the length is almost justified by the amount of content in it despite the consistent riff/vamp nature of the song due to the variation in the instruments that are not the rhythm section (although I do still think it's slightly longer than what is justified)
If all funk music sounds like Can. I probably would be more partial to that genre. I mean I don't automatically rule out riff music as it's very difficult to like rock music and dislike riff based music due to how central that is to the genre. I mean if I took anti-riff based ideology to the extreme, I would have to say that Gentle Giant as complex as they are to suck due to them being riff based even if everything surrounding the riff is complex and dynamic and constantly changing. However if I feel that the riff is the only think carrying the tune and there isn't enough variation in mood and arrangement than it gets boring.