Honestly, I never got the hatred for sticky headers and navbars. Yes they're ridiculous if they're too big, but having the menu in an easily accessible place is usually a good thing. I mean, there's a reason mobile apps and desktop programs have menu bars rather than some other design solution.

Does that mean they're always done well? No, things like Medium's 'please join our service/subscribe to see more from [name]' are ugly and pointless, and nothing more than a visual distraction. Sticky ads (or for that matters, ads that try to take over large parts of the page in general) are also terrible for obvious reasons.

And yes, a lot of 'fancy' design techniques just hurt the usability of the page, as seen with anything that hijacks scroll/overuses parallax effects.

But I don't think sticky elements are bad in of themselves, and they can make the site easier to use if done correctly.