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?
According to many reports, lightning network adoption continue to increase. Here is an example:
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.
If Spiderchain is implemented, maybe it can be of help. It will use PoS algorithm that is proposed while not affecting the onchain which is PoW. Which means it is not altcoins but bitcoin.