Any reason you focused on only the start he made for the Sox in the playoffs after coming back from injury, and not his extensive playoff history of 12 starts and 13 appearances which is much more in line with the rest of his career numbers?
It is also worth pointing out that his 3.96 era is decently above the league average of 4.12, and ERA+ of 106. He also will always get the Mark Buehrle effect of being a very good defensive pitcher who is almost always out pitching his stuff because of that. He hasn't had an ERA above his FIP since 2016, and is about a quarter of a run ahead of it over his career. Yes he gives up more contact, but his double play rates and defense make up for a lot of that.