The taste is just plain dreadful. Not only is it bitter, the whole “sweet” part doesn’t even taste like the usual sweet you think of. Like lemonade, yes it is perfectly sweet. Soda beverages, THAT’S sweet. But TEA, awful. And it’s like no matter how many sweetener packets you put in it, it doesn’t at all help. It’s one of those drinks where you might give it another chance if it’s available thinking it might be better but it always lets you down.
Bitter sounds like hard water is altering the pH and pulling more tannins. Cleaner water, like RO water, will pull the flavonoids and fewer bitter tannins.
Second, the water needs to rest for a bit after boiling. 80C/180F is a good temp to pull maximum flavor with minimal tannins. This will again reduce the bitterness of the tea.
An easy alternative approach to tea making that will remove most bitterness is to cold brew the tea in water overnight, separate leaves and tea, and then slow heat the tea. It will have virtually none of the bitterness while keeping the flavor.
Pour the nearly boiling tea over sugar and ice cubes - clean water and slow freezing makes clear ice that leaves no flavor or residue in the tea. The sugar will melt but may require some additional stirring until thoroughly melted. Use more sugar than you might think, like 200g for each liter of tea.
Real sweet tea is a treat, like drinking candied tea.