Ahem. The "downward spiral" began in 2019 when the Sox had the biggest payroll in MLB and did not make the postseason. If you check, you will see the 2019 Sox had almost all of the lineup and pitching talent they had in 2018 when they won 108 games and the WS.
If we skip 2020, the covid season, the 2021 season--without Mookie Betts and Price and Sale--was pretty successful, which you and others always ignore. The Sox won 92 in the regular season, beat Cole and the Yankees in the wild card, beat the 100 win Rays in the ALDS, and finally lost to the Astros, 4 games to 2, in the ALCS. That was in fact a better season than 2016 and 2017 when the Sox lost 3 straight in the ALDS both seasons.
The actual downward spiral appears to have lasted two seasons, 2022 and 2023. Not coincidentally, the payroll has gone steadily down, in part because JH refuses to shell out big and long-term for great starting pitchers. Plus Mookie of course.
However, the 2024 Sox appear to be on par with the 2021 Sox and better than the 2019 Sox who still had almost all of the great talent the 2018 Sox had--and certainly the massive payroll. Moreover, the 2024 Sox are missing Sale (given away), Giolito (hired to replace Sale), Story, and Whitlock.
Nevertheless--despite the massive wailing in this game thread--the Sox pitching, over halfway through this season, is the best it's been in a long time with a team ERA, 3.65, ranked 5th in MLB. For reference, the 2018 Sox team ERA was 3.75, ranked 8th, and one of the most expensive pitching staffs in MLB with Price, Sale, Kimbrel, Porcello, Pomeranz, et al.