What @EAW was rightfully pointing out is that you are on a modern era MacBook Pro. The hardware display you are working with is not sRGB.
Sadly, the Blender development team doesn’t care, and as such, you haven’t been looking at the correct output. Worse, the proper transform is not included by default with Blender.
So that means all of your work has been output incorrectly, and when encoded, you are getting equivalently wrong output.
The only current way to rectify this is to use a configuration that supports your hardware.
You must always set your display to the colourimetry of your actual hardware display.