The Lightning Network was literally the technology needed to enable Bitcoin to be adopted as legal tender at nation-state level.
El Salvador made bitcoin a legal tender in 2021, but the country has just adopted lightning network some weeks back. Lightning network makes bitcoin transaction to be cheap and faster which is the reason it was created. If there are more people making use of lightning network, also the mempool will be less congested if compared to if lightning network is not existing.
If this has existed a long time ago and it would solve the problem of network congestion, what do you think is the reason why people are not adopting with it? If there's a way to increase its adoption, how do you think it has to be done?
Honestly, this network congestion will not gonna go away, it will happen from time to time especially if the market is quite bullish as it's expected that more transactions will be created, so we need some long term solution, unless we don't see it as a major problem yet.