Block size war is over. People who support bigger block size, but still choose Bitcoin is in minority.
It’s crucial not to let these subsequent layers become mere copies of the current system.
Mere copies? Ridiculous, many sidechain/L2 offer feature what Bitcoin doesn't.
Lightning Network is an excellent system, but I cannot truly claim to always possess my funds. Doing so would be far from simple, and I end up relying on someone else.
LN is far from perfect and only meant for micro-transaction. But FWIW there are few light non-custodial LN wallet where you only rely on 3rd party watchtower.
Liquid is cost-effective, and I hold my private keys, but the system is controlled by a few companies.
That's true, but Liquid also offer Confidential Transaction, faster block time and turing-complete smart contract.