I'm not the original guy you asked, but it's both an issue with mixing as well as the way he layers sound. Instruments get pushed way to the back, drums way to the front and vocals sit at the center of the mix, always. The main melody is always middy with no warmth, drums always tinny and weak with his 808 style, or overly fat and over processed with his boom bap style. Vocals always have the drums sitting directly on top of them, and the melody is completely detached with reverb on it which is what makes it sound hollow, and why you don't hear the flow meld with the beat. He cuts out the highest frequencies with his samples which leads to a less warm sound, and completely detaches his mids from his low frequencies. Everything sounds separated which leaves a feeling of space in the middle, and thus hollow.
Listen to these two joints back to back and you'll hear it.
Thun lacks a decent high end. There's high hats and the ESG sample, but the hats are so soft in the mix and the ESG sample is only used sparingly, and still doesn't fill enough of the high frequencies. The lack of high end is why the ESG sample releases tension, but still doesn't feel like enough when it comes in. The whole beat sounds more like a bunch of sounds slapped on top of each other than a cohesive piece of music. The violin is so far away from the drums it might as well be on a different song.
With Quantum Leap you can tell the hear the main melody meld right into the low end, so it fits right on top of the bass. The piano is front and center with the vocals and it's all sitting on top of the drums. The piano doesn't sound overly filtered, no heavy reverb, the full frequency range is present, and Alch brings in a bunch of little sound effects to fill in what gaps are left in the high end.
I fukk with Thun a lot, I think it's the best song from KD3 and one of the better beats, but the mix is off. I would have definitely constructed the beat... differently, if it was up to me.
I hear u but I just listened to both.. Thun is the better beat and the better song.