You can cook up a "pie in the sky" hypothetical about pretty much anyone. The fact of the matter is that, had the Celtics won that lottery, they were going to take Simmons. Who knows where that would've lead but you could very well argue that his temperament/personality/etc. was going to be an issue wherever he went. Fortunately, for the Celtics, this led them to taking Jaylen who has done nothing but excelled with the Celtics and been an excellent second banana to an almost annual perennial contender who is on the doorstep of a championship this season.
Not winning that lottery helped put this Celtics organization in a timeline where there have built a championship contending team.