The album has like, 2 mid tempo/slower tracks (and one of them picks up in the second half). It might not be as fast as Darkness Descends, but it thrashes in plenty.
Also, I've never heard a criticism like that about MoP, for example. An album with 3/8 fast songs, 2/8 mid tempo tracks and literally half of the album's length on the slow, not even thrash side of things.
That's because MoP is an excellent album with lots of ideas, and doesn't need to be limited to thrash.
Anyways, quick rundown listening to the album again, and blind to my autism list
Liquid Courage - first song that feels properly fast and aggressive, it's actually good too, 3.5/5
Engulfed By Flames - upper-mid-tempo, by working overtime they were able to pay off their mortgage to Metallica and splurged on a couple fast riffs in between the deliberate average ones, 2/5
Subterfuge - mid-tempo with some fast triplet riffing to create an illusion of energy, sounds like PWYP/Souls-era Testament, 2/5
Oppressing The Masses - faster drumming, relatively mid-tempo riffing, 2/5
Officer Nice - see I Profit, 1.5/5
World In A World - mid-tempo and chuggy until it reaches the bootleg Over the Wall bit, 1.5/5
I Profit - I guess technically up-tempo but the riffs themselves are slow, just with moderately brisk drumming, also that main riff repeats itself way too fucking much for such a boring riff, 1.5/5
Mentally Afflicted - see above except replace Over the Wall with something worse, 1/5
Previous autism list:
Subterfuge - 3/5
Liquid Courage - 2.5/5
Engulfed By Flames - 2.5/5
Officer Nice - 2.5/5
World in a World - 2/5
Oppressing the Masses - 1.5/5
Mentally Affected - 1.5/5
I Profit - 1/5 (really boring)
So aside from being able to appreciate Liquid Courage this time around, perhaps as a result of listening to the album for the conscious objective of finding up-tempo/energetic music, I stand by my original assessment more or less.
Also, nearly every drum fill sounds like it was stolen from Tom Hunting.