"There is no reason in the world why you would not use some other blockchains or cryptos as well".

I am a normal human being, work hard, take care of my family, own a home, own some stocks, save in bitcoin. Why in the world do I need to use some other blockchains or cryptos?

This is the crux of the problem, the feature set of ethereum and other chains is not really needed by the vast majority of people. Sure if you are a trader, speculator, technologist, or arbitrager, you might have some use case but most of the world doesn't need it.

The best argument I can see for Ethereum or other chains to have any sort of future is the movement of stablecoins. I mean, I guess being the rails for future CBDCs could be a pretty huge TAM, but I thought escaping the corrupted system not embracing the corrupted system was the ethos.