Reading tea leaves is a form of divination. You would have to use actual tea leaves in order to actually get some symbols. As with all divination all that matters is you, it is you and your brain who is going to make symbols out of the tea leaves, not the tea leaves themselves. Our brains are hardwired to organise and interpret a chaotic mess into patterns and symbols we understand.
It doesn't mater if you use tea leaves, Chicken intestines or clouds. It is all about bypassing the conscious mind and accessing the unconscious mind which communicates in symbols.
Whilst reading tea leaves may have been created as a gimmick, I would argue it would work as good as (or not at all) as other methods because it would work in the same way.