This isn't just a Syracuse problem, though, is it? Can't you say the exact same thing is happening right now at a lot of different schools - like Villanova, for example? They haven't been able to land any top PG prospects since Gillespie took over that role - he basically plays 35 minutes every night. He's Jay Wright's guy, no question about it. And when Gillespie is finally gone next year, Wright will either have to either re-load with a true freshman or go out and get a PG transfer.
Carolina has been dealing with this lately, too - they had back-to-back freshman point guards with Coby White ('18-'19) and then Cole Anthony ('19-'20), and not a lot of depth behind them - because what top-level kid wanted to go to North Carolina and ride the bench behind those guys? And when Anthony got hurt, they had nobody on the bench and their worst year in a long time.
I just think that the world of college basketball is way different now than it was even just 5 or 10 years ago. Transferring is much easier and much more common - and most kids simply don't want to go to a top-tier school and wait their turn for 2 years. We're just not gonna see many career trajectories like Lazarus Sims' any more...
And for what it's worth, most of our recent transfers haven't gotten more minutes at their new schools. One could argue that Brycen, Jalen, Woody, Moyer, or even Taurean would have all been better off staying at Syracuse - because they likely would have gotten more minutes in successive years as they improved, and as Boeheim trusted them more.