0.6% is orders of magnitude larger than the percentage of people who have a legitimate use case. In my opinion it's not that coin does not have legitimate uses, it's that the cost of providing those uses far outweighs the benefit by design.

The current increase in value and ramping up of energy use is not due to an increase in the usefulness of the coin, but instead on a renewed interest in the game of hot potato that is speculation.

Exactly, hoarding bitcoin —not using it— is the problem. It leads to high prices and consequent high environmental impact.