The Red Sox drafted Pedroia, Bradley Jr and Betts. They signed Bogaerts. They signed Moncada which enabled them to trade for Chris Sale. By winning they consistently have money to spend, ala David Price, Hanley Ramirez, and JD Martinez.
In order to get to the point where they can sign vets, they need to establish a young foundation (Kopech, Moncada, Anderson, Collins?, Jimenez, Zavala, Gonzalez, Burdi, etc). When that time comes and the park starts to fill up, they'll add vets in. End of story.