I jumped on this bandwagon long back for preventing horizontal scrollbars and other issues. Is there an updated advice for allowing zoom and being responsive?
Preventing zooming is a serious accessibility issue and it makes the content worse for every user.
If you’re properly setting responsive widths, a large enough base font size, large enough input text size, and using border-box for box-sizing, things should just work except for cases where you’re absolutely positioning things or telling them not to word wrap and they are wider than the viewport.
Quick tip: Make sure all of your inputs are at least 16px font size. This will prevent most mobile browsers from “automatically” zooming in when an input is focused ;) Which is a common reason people employ the maximum-scale property.