> I can't even get through Easy on DDR because the arrows move too fast

The trick to basically all of these games is not to actually try and look at the arrows. There are a lot of them, they are moving fast, your conscious mind can't actually track and respond to each one of them individually.

But with practice you can train your self to more-or-less automatically respond to the sequence - there are only a handful of variations, and you learn the patterns that they typically arrive in.

(For a little while I had too much free time on my hands, and was in the top-100 BeatSaber players)