As is the case with most first DDAs, this is powered entirely by launchpads, and that's a bad thing. Launchpads are predictable, they're too easy to use, and they're boring. If you carefull watch highly rated DDAs, you'll see propulsion by way of doors, thwumps, and bounce blocks.

It is not enough to simply throw enemies into a level, and more rockets is rarely better. Each enemy should have several close calls with the ninja. Many of the rockets in this map flew straight into walls without ever coming near the ninja.

Unnecessary enemies are bad, but excess objects are worse. Every object in the level should be hit at least once and have a real purpose.

On the plus side, having a theme (in this case, the pyramid), is definitely a good thing, and one which many DDAs lack.

Finish the borders
Dont use launchpads (if needed, use, but not so many)
Dont put so many enemys
Remove the unnecesary things.