One thing I don’t like about the protocol is that LN nodes must stay online or risk having the other parties of their channels steal their funds. I know there are watchtower services to help guard against this but needing to trust a 3rd party to make sure you don’t lose your money goes against trustlessness, a core principle of cryptocurrencies. This is the reason I abandoned the idea of running my own LN node. I didn’t want to risk losing money in the case of an extended outage of my node.

1. All payments have to be routed across channels of arbitrary size across an arbitrary network. It's a small travelling salesman problem that only gets worse as the network increases in size.

2. It requires a transaction to L1 to open/close a channel. If 1B+ people used it the Bitcoin network itself couldn't cope with that. At 7tps it can handle a max of 220M transactions per year.

3. You need enough liquidity in all channels to your destination to send a payment. This is fine for micro transactions but it can't handle $1k+ transactions well at all.

4. You have to re-balance channels or they stop working.

5. You need some sort of watchtower / guardian node to prevent the other person from being able to steal your funds.

ZK-Rollups completely obsolete the lightning network. If Bitcoin did a hard fork to make them possible every single person would migrate to them. Lightning is not a long term solution, it's mostly a meme to throw back at people who say Bitcoin doesn't scale.