Backups and security. I wish we wouldn't have to worry about them as much. If I could choose anything, even unrealistic things, I would want the Lightning network to be as simple as on-chain: Backup your keys properly and you'll be ok.

I think we're on a good path with Eltoo (which eliminates huge parts of the headache that backups cause today) and things like the Blockstream's Greenlight and VLS.