JBJ was our starting centerfielder in 127 games in 2014 but he ended up in Pawtucket because his OPS was .531. Today it's .545.
What keeps JBJ on the field is the top 5 or 6 in the Sox lineup. The Yankees have a new murderers row this year and lead MLB in runs scored with 185, but the Sox are second with 180 and our current top 6--Betts, Beni, Ramirez, JD, Bogaerts, and Devers--are better than theirs. The Yankees bottom third of the lineup is way better than ours.
The 2014 team could not afford to keep JBJ in the lineup, but this team can. And it isn't just JBJ, it's also our two catchers and Nunez/Lin/Holt.
When Moreland with is OPS of .984 plays 1b, JD goes to LF, HanRam to DH, and Beni replaces JBJ, the lineup gets even better because Devers drops to 7th. But so far Cora hasn't done that very often because the lineup has been so productive despite that bottom third whose best bat currently is Nunez with an OPS of .646. His DWAR, it should be noted, is -.4.
Back to JBJ. I do agree with you that it makes sense to give JBJ more time to get his swing back to something near 2016 when his OPS was .865, Ortiz was anchoring the lineup, and a bunch of guys had good years they didn't have last year, 2017.
You in fact predicted the lineup would bounce back this year and not just because of JD, and you were right. So there is hope for JBJ.