Equally important are:
Blend of Tea chosen: Not just Red vs Green etc. Personal preference largely.
Temperature: A problem at higher altitudes for open "kettles" to get 100 C
Water: Pure distilled deionised isn't nice. The water has to be just right hard/soft. The sort that only causes very slight limescale, not too much nor none. I think water from peaty or granite source isn't as good. Obviously should have no taint from excess chemical treatment. But this may be personal preference.
Oxygenation: Water reboiled too much is too low in dissolved gas.
Brew Vessel: (pot or cup, Metal, type of china, Glass, etc)
Brew time (also on Stove or natural): Depends on personal preference
Cup : A cup only used for tea. Different kinds of tea seem nicer in differing styles of cup / mug.
Additions: Natural, Milk (low, normal, UHT, condensed etc), cream, whitener, Lime, Lemon, Rancid Yak butter, sugar etc are in the realm of personal preference. I prefer tea with only water, or occasionally lemon or lime slice in certain red (black) teas.
See also Chai