It hit me hard, when I saw my user's screen which was relatively small and my sidebar and header were both sticky, leaving only a small area to display the main content.
I've now gone back to mostly non-sticky elements. It's refreshing. Not seeing those "frequently accessed" elements isn't much of an issue. I don't think I ever complained about popular websites not having its header sticky.
Letting users focus on the main content has been by far the most beneficial thing from my perspective.