You do have a point, but I believe that you're missing the big picture there my friend.

Internet had some issues to be considered mainstream in the nineties and that was because it had many infrastructure problems. Blockchain as a whole will face the same issues, but imagine how hard it would be if we wouldn't even have bitcoin (today's largest blockchain infrastructure). Bitcoin is helping us to gain mass adoption and, despite I feel the same as you do (it won't hold in the long run), I believe that right now we all need a healthy Bitcoin, for the sake of every other altcoin. Don't you agree?

On the other hand, infrastructure (energy) costs won't be mathematicaly positive in the costs equation till we start having real use cases for the majority of blockchain projects. And ultimately those projects would never even exist without the infrastructure.

So, let's keep the energy flowing for a while longer, it's a long term game. And a game that will be won by the blockchain, no doubt about it.