Losing JBJ, and finding a reasonable CF or RF (can't be picky) should not be all that difficult. Travis has probably shown enough to plug him into a corner as a worst case.
This year I think is a bit of an aberration, in that the pitching was all bad at the same time. The only exception was Rodriguez, and even he was more an "above average" outcome than a crazy outlier. I guess I should say Workman as well.
Position player wise the team is fine.
C: Vasquez - Quality Starter
1B, 2B: Open to ideas
3B: Devers - Sure looks like a Superstar very soon
SS: Bogaerts - A not quite superstar
LF: Benintendi - A very good player, if not quite a star
CF: Bradley - decent starter
RF: Betts - actual Superstar
DH: Martinez - A not quite superstar but absolute stud