To fund a Lightning channel you have to pay fees on the Bitcoin network, which can get quite high. Up to 50 USD during times of high demand.

To send to someone who's offline the recipient either has to run their own always-on node, or use a custodial service.

Routing small payments (one of the goals of Lightning) is unreliable with a high chance of failure. See http://essay.utwente.nl/82015/1/Satcs_BA_EEMCS.pdf

The paper linked is called "Understanding the Lightning Network capability to route payments" which cannot be found in any reputable or peer-reviewed journal. How is that suppose to be a reliable study?

Sure, give it a try. Let me know how it goes.

I've been using Lightning on sites like coinpayments and others for months. It works perfectly every time.

Again, I'd like to ask you, what doesn't work?

This does not show that the lightning network doesn't work. It shows that lightning has less locked value than Ethereum's layer 2. Incentivize yield farming is likely the cause.

In terms of lightning being usable now, I've been using it for years with no real problems, both as a merchant and as a consumer.

This is some shit poster that wouldn shill some currency like nano or Bitcoin cash I guess. Lightning works fine. I've been using it for past year with zero problems. Check blue wallet, phoenix wallet, bottle pay, strike, opennode, lnmarkets, kollider, sphinx chat

If you're highly motivated and technically expert, you might be able to get non custodial payments to work on lightning. Even then, your experience may be something like this - https://threadreaderapp.com/thread/1376286470256873475.html

You don't need to be a technical expert. Go to getumbrel.com and follow the instructions