When McCarthy was starting out in the middle decades of the 20th c., there were more of those editors who could do what Erskine did because they had the skill to recognize talent, the patience to stick with it, *and* the clout within a publishing house to persuade the firm to go along.
Another famous example is Robert Gottlieb, then at Simon & Schuster, who picked up Catch-22 after it had been rejected just about everywhere. Publishing is so much more market-driven now.
So I suspect what McCarthy would have done without Erskine is eventually to find another editor, maybe at a smaller house than a behemoth like RH.
One of my biggest concerns about the self-publishing boom is that even if authors do make money — a big if — they’re typically forced to be their own editors so they lack the perspective of a great editor who could help them raise their abilities to a higher power. It’s a real conundrum.