First of all, I'm not trying to attack you or anything, I'm genuinely interested in your reasoning behind some of your opinions.
While I think all the early Norwegian bands had their own somewhat unique sound to some extent, I don't think that DMDS is significantly different enough from a lot of black metal to think it's great and the others are shitty. A song like "Pagan Fears" builds atmosphere through subtle manipulations of its main riff and repetition, a hallmark of lots of black metal.
Most of the black metal I've heard doesn't put in nearly the same effort to build a song, and even when more repetitious I can appreciate it in small doses. Pagan Fears also has a pretty busy, almost technical intro, and is just barely over six minutes long total.
"The riffs are completely different"
Some of them perhaps, but it's full of those tremolo melodies featured in a huge amount of black metal, many of which are directly influenced by this record (or more likely, earlier versions of songs that ended up on here). I find these riffs to mainly be vehicles for creating the dark and creepy atmosphere, again like a lot of what the genre aims for.
Mayhem definitely invented the fundamental second-wave riffing style, but I'd still say there's a lot more diversity here, and I give the more repetitive songs a pass partially just on the basis of how ground-breaking this stuff was in ~1990. Even so, the riffs seem more nuanced than most of what came after in the style. They almost never repeat a riff more than four times before changing at least something in the song. Compared to something like Gorgoth's Katharinas Bortgang where I'm listening to nearly the same thing the entire song aside from the chorus, it's night and day. Mayhem actually created textured and subtle music. Later second-wave black metal subverted that by creating boring verse/chorus music with very repetitive riffs, and calling it "minimalist" for suckers. Bands like Hate Forest would bring the style to a point of no return.
"it doesn't force-feed the listener "atmosphere" through 10+ minute songs"
Ok, so what? Plenty of black metal doesn't do this. You didn't initially mention Emperor, the songs on the Emperor EP, and ItNE have similar lengths to DMDS tracks. The first 3 Gorgoroth records are full of short, to the point tracks, but you think they're terrible.
I actually enjoy some of the Gorgoroth I've heard, mostly just the first album I think. Half of that is probably Hat's vocals but whatevs. The really short songs are often pretty bad; to the point, but their sense of melody development isn't remotely on par. The most repetitive song on DMDS blows away something like Drømmer Om Død with that garbage hoedown 8th note main riff, and then when they try a bit more melody in the inter-verse parts it just treads the same In the Nightside Eclipse ideas that were basically already established on Funeral Fog. Gorgoroth is kind of the quintessential second-tier band of the Norwegian scene to me, much like Heathen to Bay Area thrash or Massacre to Floridian death or something.
"the drumming is more dynamic"
Compared to what? Transilvanian Hunger? I don't think this is valid, DMDS is still extremely heavy on the blasting. Hell, my 2 favourite tracks (the last 2) are pretty much just straight up blasting for the duration.
What do you think of the early Greek bands like Rotting Christ, Necromantia and Varathron. I'd consider them to be quite riffy black metal.
Give me some examples similar drumming in black metal. I don't know any others where the double-bass plays as big of a role, for example; sure there's a lot of blasting, but any time it slows down a bit it's surprisingly involved. Even when it is blasting, Buried by Time and Dust is so damn intense in a way that most others can't match.
I consider Varathron to be pretty good, but I think of them more or less as a trad metal band with a black metal aesthetic. I haven't heard a Rotting Christ song I thought was even ok, but they're kind of a similar case from what I have heard, really bad trad/power melodies with amateur performance.