I agree that small market clubs always have a problem with attendance, but, even given that, the Rays stand out as the consummate team with ridiculously low attendance.
At the upper end, big market clubs, they will probably always do pretty well with attendance.
As for the Red Sox, I'm less sure. For example, their average attendance in 2017 was 36,029. The next season, 2018, probably the best Sox team ever fielded with 108 wins, the attendance was 35,747. It should have been easily over 37,000.
This year I'm hoping the low attendance, 30,763, is the result of really nasty weather. Last year it was 32,408 (for the season) even though at this point last season the Sox were 10-17.