I feel like the quality is almost there on this one. I think you could use a better piano VST than whichever one you’re using which to me sounds almost completely mono. Stereo piano usually sounds nicer in a track like this.
Those rhythmic syncopated strings hurt the overall track instead of helping it, IMO. They sound too robotic as others have mentioned and just stick out of the mix. Either use a higher quality library for the strings, decrease the velocity so they aren’t so loud, or just take them out entirely.
As far as the overall mix it’s kind of mid heavy but it’s not terrible. That square lead pluck fill that happens occasionally is a bit too loud in the mix I think. Bass could be a bit louder but I’ve heard other tracks on here with similar bass levels that got accepted.
I don’t think your problem is loudness at all actually. You could actually increase the overall volume by a few dB if you wanted. Increase by like 4 dB and put it through a Pro-L and it will be pretty competitive at that volume with other tracks here.
Anyway I think if you replaced the piano with a better sounding piano (LABS soft piano or Alicias Keys for example), removed/improved the strings, and used EQ to cut the mid frequencies where it’s peaking, then boosted the whole thing by 3-4 dB into a limiter, this track would be easily accepted. As it is, it’s pretty close to accepted quality anyway so these are just minor adjustments.