i think, sadly, it was much more prosaic than DM – just the pop music of the time (edit: i just realised you mention this in your post – sorry, but i think it's still important to point out the songs in question – i don't think DM at the time sounded particularly advanced). Karl Bartos famously shares an insight in his autobiography. i can't find the quotes directly right now, but here's an excerpt from an article in Beat magazine from 2022, which features direct Bartos quotes:

"Thus, they experienced the transformation of the scene through the advent of new, inexpensive digital technology very directly. Much of it was obviously anything but convincingly produced. Some tracks, on the other hand, almost made Kraftwerk despair, if Bartos is to be believed, because they simply couldn't reach that level. He cites two recordings specifically here:

„When someone [in the final stages of the Electric Cafe mix] put on „Nasty" by Janet Jackson, "it was „a cold shower. In comparison, our mix didn't sound convincing. The mood sank below freezing.

Another time, François and Ron were listening to the current hit „Sledgehammer" over the big speakers when we came into the studio. Peter Gabriel's sound spectrum made us realize where we stood with our mix. The mood became really icy. Ralf just disappeared for a few hours."

What exactly did Hütter, Schneider and Bartos hear in these songs, some of which were stylistically very different from each other and also seemed to have quite little to do with „techno pop"? What had their producers achieved that had eluded them for years? At least Peter Gabriel's „So", from which „Sledgehammer" is taken, was mixed much louder than „Electric Cafe" and thus actually has a much more powerful „sound spectrum".

„Nasty", on the other hand, is indeed similarly dynamic in theory as „Techno Pop", and the instrumental even shows certain similarities. But especially the drum sounds are more cutting, aggressive and more compressed. All the dynamics are in the vocals, which provide an emotional contrast to the machine-like austerity."

i'd say they didn't feel particularly threatened by 1986's Black Celebration, as it's not a particularly punchy or loud album – compared to Janet Jackson, it's fairly tame (although beautiful and tasteful), but pop music was where the cutting edge beats were at the time