Any first time distributor with a 50+ million opening is going to miss some opportunities but every other first time distributors and even well established ones would kill for the performance they did get.
What I think that AMC/Taylor Swift missed some opportunities on:
The 6pm Friday thing was stupid. Thursday pre-opens at 6pm Thursday should have been a thing from the get go. That is fixed with Beyonce.
Taylor Swift did very little to specifically promote outside her social media channels, as far as I know her "surprise" SNL appearance and Premiere appearance was it when she had full SAG-AFTRA waiver clearance to do all the talk show rounds, etc.
At the very least Taylor Swift/Adam Aron should have been making the rounds together (I get that the blackmail court case leak right before opening wasn't ideal, and that Adam Aron is not exactly universally beloved with his fanbase after their stock moves in the past few months)
AMC spent very little on marketing and well, if you look at their social media channels, etc, put very little effort on them as it is. On the flip side to that though they would have likely had to do a standard $20-40 million marketing spend to get an extra 10-15 million, maybe?