You Keep Me Hanging On, recorded in 1966, is Jamerson changing the world of bass from a supporting role to a feature at the front of the mix. It's not really "fiddly", he took that to another level with songs like Darling Dear and For Once In My Life, but it's busier than bass lines were up to that point.
If you're having trouble with any bass line you can slow the YouTube video down, go to settings, or check out the "how to play" bass cover videos.