While the prospects ferment, I've never believed teams in a rebuild shouldn't use resources to sign or trade for an ace pitcher.
Don't wait for a window -- a big league ballclub has a responsibility to its fans to open one!
The Red Sox finally did that with Crochet, but make no mistake, this team is still in a rebuild. They have what looks like a promising group of young pitchers, decent catching, and some above-average all-around outfielders.
But they're also missing a major league infield, quality contact in the batting order to get them to another postseason, and more longball threats to make a deep run in the playoffs. A really creative CBO might be good enough and lucky enough to make moves to acquire primetime players with multiple skills that overlap all those needs and expedite title contention -- but nothing is guaranteed...
... except you can't win the lottery unless you buy a ticket.