I love the drums and those speaking bits are pretty cool. However, I think the melody and bass synths sound too similar (perhaps they're exactly the same?) I suggest for the main melody that you have something that sounds more like a theremin (a continuous sine wave, so no plucky envelope, and monophonic with note sliding). It'll sound spooky and spacey.
There's a long "silence" where I presume is a verse, and it feels like the longer chord-like sound came in too late. But I'm not very worried about this, because if there's going to be vocals later, then you can more than make up for a "lacking" instrumental. It would actually be weird not to have space for vocals in a song's instrumental.
There's a part at 1:25 that has four rhythmic melodies happening at once, which seems kind of crowded and imbalanced.
Anyway, the overall idea seems really interesting.
There's a vocalsynth music production discord, so if you're interested, you could join~
https://discord.gg/hjjbaQQ