I don't really know what you're trying to say, but my child seems absolutely able to pick up modern UI design, including the hamburger icon and others, and use it very happily and with joy.
Kids would be able to pickup CLI if that were the only way to start their favorite game. Kids also share knowledge even when your attention is away. We had a drive to learn MK combos and used that to win fights, but as adults, barely anyone in a random-100 group knows how to :q Vim.
Give your kid a phone with zero interesting activities in it compared to other toys, and he/she would “pick” nothing out of it.
> Kids would be able to pickup CLI if that were the only way to start their favorite game
This is not merely hypothetical! Like many on HN, no doubt, I learned at least how to launch and close my favorite toy programs from the DOS command line before I went to kindergarten.