Putting a rechargeable, non replaceable lithium battery in a new version of a device that used AA before is not an upgrade.
Modern rechargeable AAs are cheap and last plenty long enough. And even if the lithium battery was replaceable, it will often be an unneeded proprietary change that'll cost more than it should.
Standardized replaceable lithium batteries should become the norm really. I get why you don't want the average person messing with an 18650, but you could make packages that have decent protection circuitry, that stuff is so cheap these days.
@noiob Seeing someone complain about that was exactly what got me to write this post 😆