Yes.
Which is all to say that John Tavares's decision to go to free agency set a chain of events in motion that allowed NYI to benefit from opportunities they were lucky to be presented with. It really illustrates how consequences, good and bad, are unforseeable. Still, it is not John Tavares's absence as a hockey player for NYI that explains NYI's success or Toronto's relative failures. It was forseeable *at the time* Tavares signed that Toronto was overinvesting in forwards. (I and many others said as much at the time.)
I'm not saying that they would have gotten him, but I do think that a hypothetical Toronto roster that were to contain Alex Pietrangelo instead of John Tavares would be a better playoff roster than the one that just failed, and also that I do not think that is an insult to John Tavares. Fit, and roster construction matters.
I thought, before that offseason (before 2018-2019), that Tavares should join the Blues. Obviously they got O'Reilly instead. I thought at the time that STL would have been JT's best shot at a cup.