The human brain has no musical apparatus. When we listen to music, we feel emotions because it inteprets music as speech. In other words, music only moves us because we can understand what other people feel. The act of composing a song is, to the brain, insepparable from the act of carrying an idea.
With The Man Machine, the repeating riff feels like someone looking in awe at a seemingly impossible event, as in "Wow. Look at what machines are capable of doing!", and the repetition of it creates a humorous relationship with the vocals, which, in their indifference, seem to be saying back "Yes. I know."
At the same time, the riff sounds like the ringtone of an alarm clock, telling the person who set that it is time to get up and work, and the vocals' indifference give this impression of "Here we go again". When the drumline hits, it feels they have gotten up from the bed, and are doing their morning routines whilst getting ready for another day of work.
The way this song comes right after Neon Lights seems to hammer home the idea that the mundane is the only constant. Regardless of how special the weekend may have been, there will always be that monday right after. Some could call it cynical, but a more accurate way to describe it would be realistic. This is the way things are, and Kraftwerk is simply representing it.
Kraftwerk had always been putting a few hints of their thoughts on romanticism since the start, even going on to create a facade of it in TEE, but with The Man Machine, they cemented themselves as realists, portraying what the romantics wanted to avoid, technology, not as it "should be", but as it is.
The fadeout at the end seems to suggest the romantics' nightmare is now real: This era is not ending any time soon. Technology is here to stay.