A couple things to consider here:

The first song from "Maoist" isn't from Mao's era at all. While I couldn't confirm, the album art in that YouTube video seems to indicate 1990 as the date. So it's not that it "sounds" more modern than USSR/DDR music... it simply *is* more modern than the USSR/DDR music that I'm guessing you're referring to. Regarding the North Korea video, I also couldn't confirm the date but based on the synth instrumentation and the video shots, it looks like it's also from the 1990s.

Second, what do you mean by USSR/DDR music, exactly? Certainly, the music of the Stalinist era sounds very antiquated to the modern ear, such as this gem from 1950s DDR, Teil 17 Stalinallee (Section 17, Stalinallee): https://youtu.be/1q192aOva7w. But this is a very limited example from a very specific era. By the 1970s and 1980s, music in Eastern European communists states had evolved quite a bit and sound much more modern. I don't have any links to USSR/DDR songs in particular (not my specialization) but here are some examples from Poland and Yugoslavia in the 1980s. The Polish Band Turbo's song Kawaleria Szatana (Satan's Calvary): https://youtu.be/O2kqyOiWaFk and Riblja Corba's song Kako Je Lijepo Biti Glup (How Beautiful It is to Be Stupid): https://youtu.be/cqsmoe57kCk

Now, these songs do not 1:1 represent "the state's" music because they came from an era where state control of the music industry, and the culture industry more broadly, had greatly loosened compared to the 1950s. In that sense, they aren't official state propaganda songs like the Chinese and Korean examples you listed above. Still, it's worth considering just how modern music was under state socialism in Eastern Europe.

Not the most direct answer, I know, but hopefully some good food for thought :)

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If you'd like to read up on rock / punk / metal music under state socialism, I'd recommend the following articles:

"Clashes of Emotions: Punk Music, Youth Subculture, and Authority in the GDR (1978-1983)" by Juliane Brauer

"The Communist Culture Industry: The Music Business in 1980s Poland" by Raymond Patton

"The three phases of rock music in the Czech lands" by Sabrina Petra Ramet and Vladimir Dordevic

"Soviet 'Flower Children'. Hippies and the Youth Counter-Culture in 1970s L'viv " by William Jay Risch

“This Is a Country for You”: Yugonostalgia and Antinationalism in the Rock-Music Culture of Bosnia and Herzegovina " by Zlatko Jovanovic