No Sugar Tonight in My Tea
Do what you like, really.
Personally I never add sweetener or milk to mine, but that’s not because of any sort of purism or snobbyness. I just don’t like it much. Some people think that a bit of sweetener can emphasize flavour notes already present in a tea, but to me the addition of sweetener only tends to end up as a rather strong astringency. I can take milk in tea if that’s how it’s served to me, but I prefer it without. (Unless it was brewed by Husband’s sister because she tends to go for builder’s tea and doesn’t always remember to stop the steeping for others)
Experiment with additions. See what you like and what you don’t like, and when you have found your perfect levels of sweetener and milk or none at all, then continue to do that. Don’t let anybody try to have you believe that you’re doing it wrong. There is no wrong way. Others can’t taste with your tongue, therefore they can’t make value judgments on your preferences either.
If anything, I add honey or stevia / xyla (xylitol product). 95% of the time though, I drink it straight. You just have to watch the steep time; no GOOD tea should be undrinkable to the point where you’d have to fix it or add milk to calm the tannins. There are many inferior black teas where you have to dilute; with a good one, there should be a lighter taste that you can enjoy straight. I find milk masks tea flavor and should be used only with certain types of black tea, maybe Irish/English breakfast tea.