You're not wrong, in fact many L2s are controlled by single entity. Linea and base is among the most centralized blockchain.
Linea have centralized sequencer controlled directly by the foundation and also the governance is foundation-led. At least the other L2 only have security council but this one is pretty much centralized.
It's no wonder why most L2s are able to offer ultra-low fees and blazing-fast speeds. Because they have sacrificed decentralization in favor of convenience. Even Bitcoin's Lightning Network is in the same boat. Guess what? It turned out to be a huge failure. With so many altcoins available on the market, people can just switch to an altcoin of their choosing instead of an L2 network. It's much easier this way.
I guess L2s will become useful when the main Blockchain becomes too crowded. Considering that demand for crypto has stalled a bit, it's going to take quite a long time before we see a resurgence in L2 usage (if any). At least we know, ETH will outlast many L2s and "shitcoins".