Plenty of teas aren’t even made of leaves.

Then it’s not tea, it’s an infusion or decoction.

Tea is made from a specific plant, the tea shrub (Camellia sinensis).

These infusions might be called tea, but they are tea in the same way as a hotdog is a heated companionable mammal.

Asian cultures called various hot beverages tea 茶 before some Westerner decided that they are wrong. Sure there is green tea from that plant but Asian cultures also had mint or chrysanthemum tea using the same 茶 character (pudina chai in India for mint tea).

If anything, the Westerner who decided that beverages made from only that specific shrub is called tea was the wrong one. Broader uses predate your definition.