I guess you don't know that other popular lemony drinks like Sprite and 7 Up also don't contain fruit juice?

very similar to Mountain Dew I think

Not that similar, Mountain Dew actually has fruit juice in it.

No offence but it sounds like you just looked at a soft drinks can label for the first time today. I'm British as well so it's not like I'm being defensive about the national drink.

This is kind of like if an American went to Glasgow and starts complaining that IRN BRU is too sweet and sugary. I mean what were you expecting? Is NZ retroactively not allowed it's own traditional brands of soft drink because it doesn't lie in with some healthy and green image modern tourists want to hold on to?

Looking forward to your post about how traditional kiwi pies are very similar to a Mcdonalds Cheeseburger