This game is combo based, cursor movement relates to combo while streaming relates to accuracy. If your aim is good then you can FC lots of maps, then again you will probably fail at stuff like chipscape, but it's not like there are many maps like that. Then again if your aim is bad, even if you're a godlike streamer (see KeigoClear) you gonna have trouble with lots of maps, failing to FC even while getting top tier accuracy. Of course, other players gonna have a lot of trouble beating you, but then again you gonna go mad trying to FC any kind of hard map + mods since all of them end up requiring very good aim.
Both are important, but if I had to choose godlike aim or streaming, I'd get aim, no doubt. Remember how those most impressive scores you see from Niko, WW, Cookiezi and rrtyui are pretty much aim based. Even if their accuracy is great too, there are some other players that probably can get the same accuracy as them, but yet they can't do it because their aim is not good enough.
Freedom Dive is not hard because of 300 hit long 222 BPM streams, not at all, the stream practice version is way more exhausting and demanding than 4D, yet it is way easier to clear.