You’re right. Each branch was intended as a check or balance. Go all the way back to Marbury. SCOTUS was concerned about it’s ruling being flat out ignored.
Marshall's main point in Marbury was that the courts must follow the Constitution, no matter what any other branch does, just like the other branches must do.
Definitely not what the law schools or the lawyers or the politicians generally promulgate today.
If Marshall had tried to push anything at all resembling the sort of nonsense they say Marbury represents today, the founding generation would have impeached and removed him and anyone else who agreed with him, right before they ran them out of town on a rail.