I've been saying this same mantra for years, but I'm starting to shift my opinion on it.
Yes you can trade hitting for pitching, but you can't get away with that to build the majority of your pitching staff. Yes we've developed our own guys who are good E.G. Houck. But not enough high end talent. When is the last time we developed an ACE?
Sure we can trade for one, and perhaps we should, but if you're trading 4 for 1, or 3 for 1 prospects for pitching, eventually you're going to have no team on the field behind them. Prospects bust, but some don't, and the more bullets you fire the more Bogaerts, Betts, Durans, Casas, Bello's, Houcks you're missing out on. I know the talent level varies on that list, but you need good to better talent all up/down your roster to compete for championships.
At some point, the Boston Red Sox are going to have to do a much better job of bringing in elite pitching talent, Whether that's trading for younger pitching prospects who they can better evaluate and develop (a good example of this would be if Fitts develops into a #3) and/or drafting pitchers via Rule 4 and IFA.