* The maximum amount you can pay in a certain route is determined by the guy with the LEAST amount of money in his channel
* Users can defraud each other in a channel, so they have to continually check if somebody is defrauding them.
* Unless you have a direct channel to your target, there is NO guarantee AT ALL that you can pay the person you want to pay.
* Users need to be online 24/7 if they want to be part of a payment route. If a user is offline, this particular route is not possible which of course has huge impact on the possible routes.
* Insane amounts of data are being sent because the network needs to be aware of EVERYBODY's payment channel's state (otherwise it can't discover a route)
* You still have huge fees if you want to wire money into/outside the channel.
* It's not feasible at all for bigger payments. Let's say you have to pay $1500 rent/month, are you going to open a payment channel and deposit 3 years rent in it ? Most people have difficulties enough coughing up the next month. But if you have to wire every payment into the channel, then you could just as well pay on-chain because you're paying that exact same on-chain fee.
* It's also not feasible for very small payments/channels. If you open a $30 channel with your coffeeshop to buy a few cups of coffee per week, then the price of your coffee doubles because of the huge fees to open/close the channel. Your only option is to route and HOPE there IS a route.
* Who is going to lock up his money in several channels anyway ? Liquidity, needed for routing money, is going to be a problem
* Very difficult to use and explain to users. No way your mother let alone grandmother is going to understand all this.
Lightning Network is just getting off it feet! Just like the Internet was in the 90's. IPv4 was the only main protocol to route, we now have IPv6 implemented. Did you know DNS Resolution was a text file that was updated and sent to other computers/nodes?
Who knows, once LN becomes main stream, they may find out ways to implement a "routing table" or "BGP" to help determine payment channels. Payment channels may become more dynamic and can be open and closes freely without incurring onchain cost.
In other words, you can not say "Lightning Network will fail" without understanding all the possibilities of what this concept/technology can do. You really need to think 5/10/15/20 years from now, not what is happening now, else you may as well say Bitcoin is a failure! In fact all Crypto are failures.