I know what's missing.
And you actually called it. Not enough bass. I'm hearing the subs for sure but subs only cover so much of the low range. You need more action around 100-200hz range. Usually a good bassy pad would work for this, but make sure you don't overdo and muddy up the mid and still let the sub have some room of its own.
Regarding the subs and kick, they clash each other. I'd cut some lows off that kick (the nice subby tail sounds nice but imo it's a bit too much). Another thing is that I feel the drums are a bit... watered down, as in not enough higher frequencies for energy. I'd work on that a little bit; maybe add like a ride cymbal, maybe a hatline? Something in the higher frequency. You're also right about the melody is a bit repetitive but for this kind of music I believe it's fine so you got that down ;)
So, add a bass (not to be confused with sub bass), and brighten up the high end, I think that's what it's missing.
Anyhow this is actually pretty damn awesome xD With a couple of tweaks I can see this as a song I'd listen to frequently (good background music imo). Keep it up. :D
7/10
4/5