About any game you see highlights from, the stands are half empty.
And these are all modern, smaller parks than in the 70s, with capacities in the 40K range.
Football stadiums are almost completely full (well, for decent teams), with capacities of up to 100K.
You do know that the NFL teams fill those stadiums 16 times in a regular season while baseball teams do it 162 times in a season, right? Sure baseball doesn’t have the average per-game attendance that football does but it plays many more games.