Agree 37K is about max at Fenway (night games actual max is 37,755), but there is compelling evidence that, if you want high average attendance vs. high peak attendance for when, say, the Yankees come to town--vs the A's or some other small market team--a smaller ballpark is better. The exceptions to smaller is better are the Dodgers and Yankees because both have very big fan bases. Dodger Stadium hold 56K and Yankee Stadium 54K.
I disagree about not comparing season average attendances at Fenway because I'm just about convinced that, not only are there significant ups and downs in average attendance, year to year, but also that they are not necessarily tied to how well that team is playing that year.
More to the point, I think it's very possible that Chaim Bloom and John Henry's joint commitment to cutting payroll will continue to have an effect on attendance--and probably on TV ratings.
When the Angels came to town, April 14-17, attendances were 36,680, 36,594, 34,790, 34,942--an average of 35,751.
In the other 16 home games this season, the average attendance has been 29,516. That's a swing over over 6,000 butts in seats per game of presumably avid Sox fans who actually wanted to see Shohei Ohtani and Mike Trout. And who can blame them? The four game temperatures were 58, 56, 54, and 50 degrees.
When the Jays came to town, May 1-4, the attendances were 27,438, 27,721, 27,863, and 30,173. And the game temperatures were 50, 50, 50, and 47 degrees. That 47 degree temp game, May 4, was the one with the biggest attendance, 30,173, so I'm not sure weather temp was a big factor in this series or in April series vs the Angels. Those Jays games were all wins in the middle of an 8 game win streak, which completely failed to get Sox fans to go to Fenway Park the way the did to see Ohtani and Trout.