No, the problem is not the rotation. The problem is that the Sox have the highest payroll and by far the worst run differential, -18, in MLB.
Yes, absolutely, we're only 6 games into a 162 game season and have barely started. And this is pretty close to the same bunch of guys who won 108 last year before winning 8 of 11 in the ALDS, ALCS, and WS.
But one of the reasons 2018 was so successful was that the Sox were 17-2 after 19 games and were able to withstand a win streak by the Yankees early in the season. Now they're 1-5 and every starter is at least mildly suspect. Oh, and the lineup just got shut out twice by the A's. The Rays are in our division and have the best ERA in MLB.