You are not missing anything.
If your shooting habit/style is to zoom in and out constantly without any opportunity to focus again, you have two choices. (1) adjust your habits or (2) go back to Canon
What you are referring to is, yes, indeed called a "focus-shift" while zooming in or out. It is due to each lens' specific focusing mechanism and design and has NOTHING to do with any particular brand.
As an ex-Canon user, there are some lenses that do not shift focus, or shift only little when zoomed in or out. But I also know there are countless other Canon zoom lenses where its not he case. Its a unique design chracteristic for each lens model - regardless of brand. So you can and will have the same issue whether you go Nikon or many other Canon lenses.
Again, to answer your q on Fuji zoom lens's focus shifting, some Fuji lenses shift focus more than other models, but most Fuji lenses focus shift due to zooming in/out I know are not any more prominent than most Canon/Nikon lenses. But if its a problem for you, theres nothing missing here.
Lastly, Id just like to know - why is it such a problem? Why not just refocus?
As convenient as it may sound to not have to refocus after zooming in/out, such 'feature' usually comes at the price of sacrificing other lens design characteristics. Designing a zoom lens is a tricky proposition, and optimizing for no/minimum lens distortion and consistent quality(resolutiona, chromatic char, etc.) across zooming range typically (and often indespensibly) require some shift of focus as being zoomed in/out
