One thing I've been reminded of is that the playoffs is different from the regular season in terms of style. Teams really seek to exploit weak links defensively, and that's one reason why this debate around IT is legitimate. There was a stretch during the third quarter of game 7 of the Wizards series where IT got absolutely roasted possession after possession. Now, some of that is due to his being hurt, but it's also due to the fact that he's 5'9".
So, maybe a team without IT wouldn't win 53 games (I say they're much better defensively and probably win 44-48), but they may actually a better matchup against some teams in the playoffs.
Of course, it would be nice to have an offensive savant who's also a good defender, with size, who can not get posted up and who can swtich pick & rolls. That, my friends, is why people are enticed by Fultz.