If you look at Kane (I know, I know - just for example's sake) he's added a lot to his game in the last couple of years, at an older age than Calvert-Lewin and from a starting point where you'd have thought he was already more fully developed. And the stuff he's added to his game - a killer pass and better decision making, that ability to drop deeper and help create play, looking more complete than a classic no.9 - it didn't really look like it was there when he was 21/22, even if he was banging them in for fun and setting the league alight.
All of which is a roundabout way of saying that there's no reason to think Calvert-Lewin, who is demonstrably improving in front of our eyes, game by game, season by season, couldn't add a more productive edge to his game within the next year or two.