Converting a PDF to a png? Why? Maybe IrfanView could do that, it's what I've been using on Windows for any conversion since ACDSee went out of fashion...
I've never seen a GUI tool that works as flawlessly as pdftk. Yes, it's CLI, but it works better than anything I ever encountered.
Screenshots? You just need to find the right app, I'm not happy with the windows thing (I've been using Greenshot for a while and it's on par with whatever I use on Linux).
But yeah, my comparison is only Windows, I've never owned a mac. And maybe I'm on the completely other end of the spectrum in my perception of what "normal tasks" are.