Yes, the intention of Bitcoin is good, and as a research paper, the idea of Blockchain is very genius and interesting. But back to the use case, it must has the

Yes, the intention of Bitcoin is good, and as a research paper, the idea of Blockchain is very genius and interesting. But back to the use case, it must has the basic function first then add more features to it. With low throughput and high fee, it can barely be used widely in normal life, especially for "micropayments". Then what's the point to make it decentralized? I had some experience with L2 solution, Polygon specifically. As you mentioned, it compromises security or/and decentralization. And I don't think it's a "happy" compromise, since the weak point of a system depends on it's weakest point. If L2 chain has a security or centralization problem, then it can be exploited so that the whole system has such problem. Even if the blockchain technology can replace current banking system, it's not the solution for problems like monopoly. It just replaced the companies/organizations that are in the monopoly position. Look at the crypto concurrency exchange market and mining farms, you can get a sense. To make it clear, by "Why not let big company play the monopoly?", I mean monopoly is a bad thing, which would happen if there is no regulation. So in the system of Blockchains, we still need the regulations we need in the current system. I know there are some problems in our political and economical system, but I don't believe Blockchain is the answer.