It’s not even that it’s completely different - text emojis are more expressive. Less is more. And I’m not arguing that you can’t use emoticons in more than one way to convey different emotions or intentions, but you just can’t use :D and 😀 in the same way. Where you can use :D to be anything from snide, trolling, taking the piss, happy, excited etc you need a whole lot more emoticons to cover all that the :D can cover.
It’s not even that it’s completely different - text emojis are more expressive. Less is more. And I’m not arguing that you can’t use emoticons in more than one way to convey different emotions or intentions, but you just can’t use :D and 😀 in the same way. Where you can use :D to be anything from snide, trolling, taking the piss, happy, excited etc you need a whole lot more emoticons to cover all that the :D can cover.