I hardly send any mails via Gmail anymore since we use Outlook in the office. Although the few times I have used my personal Gmail account, Smart Compose hasn't kicked in for me yet. Not sure if I need to turn it on or if it is still being rolled out.
But what you mention about Smart Compose actually slowing you down is pretty interesting. I assume it varies from person to person. Come to think of it, this will be more useful for people in countries where English is not their first language. Not sure if Google ever thought of marketing it that way. 🤔