It used to be the case that when you zoomed a page in or out, the text would reflow to fit the page. I recall reading a bug report somewhere where reflow-on-resize was removed for performance reasons (can't find it now).
I've found browing on mobile to be nearly unusable for the past few years, because I'm forced to choose between some mobile /responsive site with no zooming or a desktop version that doesn't reflow. Is there any way to manually trigger a page render / text reflow to fit the current zoom level?