It isn't just the quality of the tea leaf/ powder in the teabag that is being called out, The method of brewing tea ruins it all. Proper tea (is theft, We all laughed, including the toaster) is made by boiling tea leaves/ CTC tea/ dust tea in water or water + milk not by dunking a teabag or 2 in a cup of tepid water for a few seconds, and then topping it with an even more tepid milk.

The Chinese brew lovely tea using loose tea leaves because the water they use is boiling hot and in a teapot, which lets the tea release its flavours quickly, and of course they don't add milk.

You can try out all methods and compare the results. Of course, if you try loose leaf tea, you might not go back to tea bags.

An advantage of loose tea is you can customize your tea blend. Eg, blend Assam and Darjeeling in 1:1 ratio for a balanced tea of strength and flavour, 1:2 for a more flavourful tea with a decent body, 2:1 for an aromatic tea that can kick like a mule. A Ceylon tea blend of nuwara Eliya tea & Kandy tea is a balm for a tired heart.