There is a thumb extension sold in Japan for such iphones.

The swipe-based navigation system on the X family actually makes a huge improvement on the old “reachability” feature of the 6/7/8/Plus. Instead of the awkward double-touch-the-home-button-without-pressing gesture to slide the screen down for one-handed use, you can actually just swipe the little home indicator down instead of up and it will do the same thing, only faster.

For some reason, this isn’t enabled by default, but it’s a big enough usability improvement that I would actually consider a large X-family iPhone because of it.

That's a good point, and an argument for why the iPhone X should've had the same screen size as the iPhone 8, just with smaller bezels.

Besides, the slightly bigger body of the X (ignoring screen size) makes it slightly less comfortable to hold in my hand.