Tea can go bad, but it just loses its flavour rather than actually going rotten (unless you're talking about a "herbal infusion", which are tisanes, not teas)

This, however, tastes like cheap kuso ocha because it's cheap kuso ocha. Go buy a bottle of knock-off Ooi Ocha and it'll have the same flavour profile; pure astringency. That's just what shitty green tea tastes like.