Unless its, say, a mapping web app. In which case, pinch-zoom adjusts the canvas map zoom, allowing regular zoom would actually break the UX.

I agree though, let me zoom on a blog post. The diagrams are often unreadable on mobile.

If you have a windows 10 laptop, pinching on the touchpad seems to give you the same zoom functionality now. vastly superior than the one built into the browser

If you're using a mobile browser on Android that doesn't allow overriding websites that disable zoom (or using a website that defines font sizes in vw/vh), check your accessibility settings, there should be a shortcut for triple-tap to enable a zoom function. Some devices have other magnifying functions as well. My tablets and phone all have the basic magnifier function; my LineageOS (android 7 & 8) tablets additionally have a screen zoom/dpi setting to modify how large both pictures and text appear, and my samsung tablet (Android 10) has this and also a text zoom function. There's also a minimum view width setting in developer options since at least Android 8, to ensure interfaces aren't too small on mobile (this only goes one way though-- there's no maximum view width and no height controls).

It doesn't help with everything, but the triple-tap zoom is quite useful.

This is one of the main reasons I prefer using a website on my phone as opposed to an app. Some apps allow me to zoom others don't. The browsers lets me do that regardless.

I didn’t know this! And inability to do this is a huge pet peeve (as well as not being able to zoom OUT and get a desktop-like view on my phone). Does this work on any browser for iPhone?

Just confirmed it works on Firefox and Safari. Though I seem to recall seeing some sites which break that functionality with CSS.