This hasn't ever been a feature of iOS. The 'Reader' mode in Safari is a similar feature if you're looking for something to make reading web pages easier.
BUT the problem is, reader mode is not their in 2/3rds + of web pages, minimum, it's not even available for this site.
Text reflow should be part of every phone no matter what make or model, it is just as important as pinch to zoom.
I think the very first generations of IOS had it (from what I have read in the past), the only reason to leave it out is not enough power to scale the text when needed or something to do with licensing, but for the price we pay it should be there. Your eyes may see good, but mine as my age and lots of people like us would find text reflow just as useful as having a touch screen on a device.
Apple needs to put it in / or back in, once you use it, you will miss it, like having power brakes, power steering, etc... That some/most don't even know what is like without.