The reason he hurts "this team" is because the owner is in a stingy phase. If this was John Henry circa 2002-2018, Masa's contract wouldn't matter and the team would be plowing forward. The only reason we talk about moving on from him is that we believe he's a hindrance to their payroll aspirations which is total BS, but it's the new world we are living in.
In theory, Masa is fine coming off the bench or as a platoon DH. In today's reality, he's preventing the Sox from getting a frontline starter.