I just replayed it to remind myself how it felt, and I just noticed the yellow raindrops! They tell you when a potential "right arrow" moment is coming up. I didn't get this before: that the right-arrow cues are on the same beat as the rain drops. it's so much simpler than I was making it my head.
My eyes were so fixated on the raindrops, but I would also try to keep an eye out on the left side of the screen on the pulsing arrows until they'd turn yellow. So hitting the arrow key felt like a scramble and like something I couldn't anticipate.
But I feel like I get it now, and playing it a second time with this in mind, it feels a lot different. I'm not sure how you'd improve anything, but maybe my lengthy explanation of my experience gives you some ideas!