I believe any milk or sugar just negates the flavours of the coffee so drinking it this way is essentially missing the point
I vehemently disagree with this. If you like black coffee, then fine, drink it, enjoy it.
But if you like a latte, then go ahead and drink them too. The quality of the coffee DOES strongly affect the flavour of the finished beverage, of course it does. As does the quality of the milk!
As for missing the point – the point of coffee, in case you lot have forgotten, is to drink something you like. And if that’s lattes, then drink lattes.
There is no ‘proper’, that’s just a term used by snobs to divide themselves between their perceived stratum and the oiks below. Why do they do that? Who knows, but perhaps it’s something to do with needing to feel above the majority…