So if I have a channel with you, and you have one with coinbase, I can buy bitcoin from coinbase through you without ever opening another channel, entirely counterparty-risk-free.
And in that scenario if you "refuse" to relay my transaction, or you try to do something sneeky like broadcast an old transaction that we made where I had .1 BTC and you had .9 BTC, that's breaking the agreement we have made and I can broadcast a counter-transaction to the blockchain proper which gives me all of the money in the channel (1 BTC).
And if I try to backstab you by broadcasting the "give me all the money" transaction when you haven't done anything wrong, you have a "counter-counter-transaction" you can broadcast that forces all the money in the channel to you (1 BTC). (and the counter-counter-transaction only works if you HAVE NOT broadcast the original transaction)
There is a bit more complexity to it, but that's the gist.
Similar with organ donations. I might not match my wife's blood type, but I can donate a kidney to some other random person if there's a network that matches someone with my wife' blood type to her.
These are all the same idea.
I'm honestly still skeptical that LN will really take off (it needs the network effect to be useful), but the idea behind it is very elegant and solid.
Bitcoin's only advantage at this point is its price, which will go away as soon as there is a crash. Then we can scrap Bitcoin, LN, and all the baggage and start with a clean 3rd generation crypto slate.
The counter-counter-transaction solves a very real problem and makes the entire system counterparty-risk-free. It's no more "overengineering" than your airbags are overengineering.
Same with trying to pay someone on the network whom you do not have an open channel with: the LN's purpose is to facilitate a network of channels.
Certainly hubs will form, but there should be many of them, and if there's a path to your recipient, you don't need a dedicated channel with them.