One-third of the league is averaging less than 20,000 for their home games:
Diamondbacks: 19,817 out of 48,519 capacity = 40.84%
Tigers: 19,634 out of 41,574 capacity = 47.23%
Orioles: 17,543 out of 45,971 capacity = 38.16%
Reds: 17,447 out of 42,319 capacity = 41.23%
Guardians: 17,050 out of 35,041 capacity = 48.66%
Royals: 15,974 out of 37,903 capacity = 42.14%
Pirates: 15,524 out of 38,000 capacity = 40.85%
Tampa Bay: 13,927 out of 42,735 = 32.59%
Miami: 11,203 out of 37,000 = 30.28
A's: 9,973 out of 47,170 = 21.14%
https://www.espn.com/mlb/attendance/_/year/2022Other than the Rays and A's, these teams play in some of the nicest stadiums in the MLB, and the Rays have been regular contenders with 2 WS appearances in the last 15 years. When you've got 1/3 of your teams who can't even fill their stadiums to 50% capacity, you have no business expanding.