Bach was a baroque composer, you are hearing the difference between baroque and classical music. You are getting at counterpoint used in baroque and homophony used in classical composition. Counterpoint has multiple independent but interrelated voices or musical lines going at once and homophony is basically the opposite where all voices or musical lines move together in a harmonic progression.

I’m super impressed with what you recognize I’ve had to do some digging and reading to even start to hear what you picked up on naturally.