Firstly, so many people drink shit coffee that how you make it is irrelevant.
Secondly, if you have half-decent coffee but put milk & sweetener in, paying double for the coffee won't help.
There's nothing wrong with putting milk & sweetener in, just like there's nothing wrong with eating milk chocolate.
If you drink it neat, then yes, feel free to spend a fortune on the beans, hand grind them and use an Aeropress.
Otherwise, here's what I do:
1. Scour supermarkets for decent pre-ground own-brand coffee. Why? Because it will always be cheap and available. If you're in the UK, I can recommend Sainsbury's TtD Columbian Quichia.
2. Buy hot chocolate (or make your own using cocoa powder and sweetener) if you like the sprinkles.
3. Buy decent milk (of the big 4 UK supermarkets, Tesco's organic is the best, surprisingly).
4. Buy a cup-sized steel sieve from eBay.
5. Buy a milk-whisk from eBay.
Serving:
6. Microwave about 75ml of milk for 45s.
7. Put sweetener in the bottom. In my opinion, Nutrasweet and clones are better than even sucrose -- the bitterness improves the coffee.
8. Put a couple of teaspoons of coffee in the sieve and poor boiling water over it.
9. Whisk the milk.
10. Pour in and add chocolate sprinkles.
The sieve doesn't need cleaning. You don't even need to empty the coffee out except after a couple of days or when it's too full. Literally tap against the side of the bin and you're done. No cleaning, no clogging up the sink, no blowing $hundreds on coffee and generating a ton of plastic waste.
My coffee beats the shit out of Starbucks et al. Indeed, unless you drink coffee neat, it beats all the local independent cafes bar who charge 15x more.