How old is your device? Discourse as a software has decided that anything running older than iOS 15 is no longer supported. As such these forums will switch to a basic view for those devices. Note that any other browsers than Safari are actually just wrappers around Safari on iOS so the only way to get a newer browser is to update to a newer iOS version. And well if you need to buy new hardware anyway, Android is a good option with most phones having community made OS versions that add new Android versions to even older devices.
See their official announcement: