Yes, the season has basically taken a dive in the last few weeks. They made something of a run a few weeks back, got close to 10 games over 0.500, but then the reality of their embarrassingly poor starting pitching set in. It really isn't complicated what the problem is. The line up is fine, they are scoring runs generally. I guess the defense and sometimes base running has not been great, but that is not the problem. And sometimes the bullpen looks really thin but that is due mostly being overworked due to poor starting pitching.
Going into the season, you looked at (or at least I looked at) Pivetta, Kluber, Sale, and Paxton and you realize that it is not a good rotation but maybe it could be OK. Yes there were young pitchers like Bello and Whitlock and Houck that you hoped would fill in but you need your core veteran rotation to do something. Of those 4 veterans, we got about a half season of decent pitching from Paxton and that was about it. Frankly it is surprising that the Sox aren't worse.
I agree that the farm system is doing fine, there are decent prospects coming up, but not enough to fix this pitching staff. They are going to have to go sign some FAs if they want to be better next season, probably over pay. They don't necessarily need to sign the absolute best, most expensive pitchers, but they are going to have to pay for some solid, reliable starting pitching.