If bitcoin really became the backbone of the world's financial system, as every bitcoiner dreams of, it will be impossible for anyone to have a transaction confirmed on the main chain. The fee price will be so high that only corporations, financial institutions and governments will have the cash flow to do it. Second layer solutions demand a main chain transaction, so it won't help. Even early adopters will be forced to move to second layer solutions.
At this pace bitcoin is becoming a tool for the system it was created to destroy.
I don't really hope or think that BTC will ever become the backbone of the world's financial system, because not every country is going to adopt it, and even if they do adopt it globally, it will be abandoned after some time just like countries are trying to become independent of US dollars (example is BRICS). Even if BRICS can't oppose the US fully but it does make some impact. Just like that if BTC becomes the backbone of the financial world then it will also be opposed by rivalries.
Anyway, I agree with you on the fact that BTC is not scalable, because it can't even process the transactions of every citizen of El-Salvador if made. The transaction process time and block size is very slow. It has to be increased if BTC wants to become the backbone of the world's financial system.
The fee is already high and the scalability problems are already showing up even if it has not become a backbone yet, And talking about L2 solutions like lightning network, which you said, not going to work, but how in what way, because it did help us to reduce the transaction fee.