Initially, I was a bit confused at how you achieved high object counts with such a short level. After peeking around in the editor, I found out how, but let's get with the review first.
0-48%
This is all grey. A monochromatic color scheme only works if you have splashes of color to make a rainbow theme (like in Skittles by Viprin) or if you're going for an ominous castle feel (like in Acropolis). However, even in these levels there are different textures and shades of gray to make the level more realistic. I would recommend adding some color and color changes to your level, as well as some new 2.0 blocks (they have good textures).
As for the gameplay, it's quite easy, which I think you were going for. However, when making easy gameplay, music sync becomes essential; there's no excuse for it unlike in harder levels. Listen to the song before building, and think about how to best suit the song. There are also numerous levels that use this song, both easy and hard, so refer to those if you don't have any ideas for a part. The ship section is also too easy; your ship section is filler (as most ship sections are), but you should make them somewhat challenging as to not bore the player. Adding obstacles to the ground and ceiling easily fixes this problem. The UFO part is fine, gameplay wise, but you should add more obstacles for both difficulty and aesthetic reasons.
Design-wise, it's too empty. From the first cube part, the thing I was wondering the most was how you managed to hit 24k objects. You need to add much more vibrancy in your decoration, or else the level feels bland. Same goes with the previous comment on colors. Cosmic Dreamer is a rather intense song with lots of colorful musical movements, and you should show that in your level. The only decoration you have in your cube part are those glowy stars that everybody uses, which is fine, but you need MORE. This applies to all your sections throughout your entire level.
Your ship and UFO's custom background is too messy. Backgrounds should be low opacity as to provide flavor for the gameplay, but yours makes itself the center of attention. Use the Alpha trigger to make it stand out less. The "frame" is unnecessary unless you were trying to add depth (in which case you should add shadows), as it only clashes with the spiky decoration pieces and the light beams emitting from the "star". It also clashes with the foreground; make sure all your z layers are set so the background is BEHIND the foreground. This will help clean up your UFO section much more. You should also try to limit the length of time the custom background runs, as there's no motion or color change to vary it up. I suggest changing parts of it at the UFO transition.
Do you need the water at the UFO section? Right now it really disturbs the visibility of the player.
Gameplay: 1/10
Design: 1/10
Sync: 1/5
48%-End
The wave part following the UFO has decent gameplay, but because there's no sync (starting from the transition itself), the gameplay itself suffers. When the song accelerates, make the player accelerate too. The block design here is also the most interesting in this level, but there are still a few shortcomings. When making a chunk of block that you need for a wave part, it's good to add complex textures and block designs here. Having all one design is ok, but it only works with specific, simple designs. Currently, the yellow blocks are irritating to the eye and the texture is an even brighter white, so either reduce the opacity and/or change the colors and/or add more designs to vary your level looks. The objects at 57% are improperly used; they're meant to be used in small quantities, not make up chunks of the gameplay. The arrows should follow the track (rotate them and make sure they're all facing forward) and the saw decorations should be used sparingly.
The objects at 65% are interesting to look at, but something should accompany them. These should also be excluded in low detail mode.
There's a massive difficulty spike at 74%, which why it is currently ranked as harder. Difficulty consistency is something you should consider when making levels, especially when the most difficult part is the end. The gameplay here, despite that, is very fun, and is my favorite part of this level. It's a bit too flashy, however, and suffers from the same problems described in the previous background. The block design is simplistic yet fitting for the background. It almost feels like a different level.
Gameplay: 3/10 (difficulty consistency is a big part of gameplay)
Design: 3/10
Sync: 3/5 (the last part was pretty well synced)
Total:
Gameplay: 4/20
Design: 4/20
Sync: 4/10
Grand Total: 12/50
Rating: Needs Improvement
Final Comments: Use the color changes to make the background color. The slopes are pointless and simply cause system lag. Same concept goes for your slow wave part: use the pulse trigger to change the arrow colors, don't build long sections of glowing objects that we can't even see. You should try to use as least objects as possible: high object counts are reserved for extremely long or extremely detailed levels, which also strive for system optimization.
Making your level longer would help with get rated. You want to be above 1 min 15 sec to have a full level that people can appreciate.
Polarbeahr kiriE 
If you make a couple more and show that you can be active, I think you're ready...