Ethereum is not for buying coffee. It's for DeFi users with very deep pockets.
Remember the blockchain trilemma where you only get to pick two out of the three: security, decentralization, scalability.
Ethereum is secure and decentralized. Hence, it will not scale well. Bitcoin has the same properties.
Yep, they strayed from what they intended to do. They've lost their way.
I think Ethereum has been successful beyond Vitalik's wildest dreams.
This is perfectly fine. No chain has to take on the massive growth in users alone. The proliferation of different chains and protocols will solve the scalability problem. Interoperability is already quite satisfactory.