Well, you haven't proven Ethereum's theoretical impossibility either. 'I think this might be a scam' is not a proof, no matter how many heuristics are on your side.
They work really well thanks to the invention of the spark plug, the carburetor, the supercharger, and decades of iteration. For many years, they were objectively terrible.
Somehow I think that at 3 year anniversary of ICE people had some actual real world use cases for ICE where ICE was still somehow better than steam engine and animals, even if ICE itself was objectively terrible?
Ethereum is objectively better in some cases. What if I want to gamble somewhere, but I don't trust websites to be honest about their odds? With Ethereum I could check the source code of the contract and be confident that it's legitimate.
A 1910s ICE might have been terrible compared to a modern computer-driven engine built on one or the other dozen million man-hours, but back in the day it was still a very useful thing that powered machines and vehicles and even had broad military applications.