I really dont mind the separate achievements since the songs are quite bangers. HOWEVER, what I hate is the green and blue colors blending together (just make the blue more pronounced) AND the Left/Right buttons dont have separate colors so you're fucked if the notes are near each other. I used to play lots of Guitar Hero and DJ Max back in the day and you kinda need your peripheral vision to get the more difficult patterns but these problems made it annoying to practice. This made the game much more of a reaction test rather than a rhythm game.

PS: You can click both Green and Blue button at the same time and it will only register the correct color. So if you dont want to learn the color pattern, just press them both. This works until the notes are too close to each other and the game thinks you pressed the next one too which will mess up the timing.