I think the concept of a wave game where your buffs are plants that need to grow in order for you to receive them is good. Especially if you have to defend those plants in order to actually get the buffs you planted and reap the rewards, but like you said in the feedback section I do agree it could be more fun. The core of the gameplay is timing left and right arrow key presses to enemies coming on screen, and the skill ceiling for that is very low, so someone that plays the game will almost immediately be basically a pro at the game, there is nothing to learn.
I think this game may actually function better from something like being a top down game, which makes it harder and gives the player more to do.
A few other notes that I think you could achieve in a 3 day time span though:
-some kind of indicator of how much health enemies have. They all have the same sprites but varying health, so idk which ones have more health
-some kind of indicator that the clock is referring to how many rounds something takes. At first I thought it was some currency that i wasnt able to see for some reason
-sound effects/music/and visual effects. Just something to look at and listen to while playing
Overall I think the idea was good but the execution could have been a little better, good submission though!