MK, in particular, needs non-headliners to keep people busy.
I mean looking at average wait times in 2024 (via thrill data)
MK average wait time: 25 minutes
EPCOT average wait time: 31 minutes
DHS average wait time: 38 minutes
AK average wait time: 25 minutes
MK already has near constant under 15 min attractions in the Tiki Room, Country Bears, Hall of presidents, Philharmagic, and COP
Additionally, MK usually has low waits on Aladdin, Carousel, Mermaid, Dumbo, Barnstormer, tea cups, and people mover.
Of the current highest waits in Disney right now, the top 5 are all NOT MK (Remy, ROTR, FOP, SDD, and RNRC)
MK holds #6 (Tron), #8 (7D), #9 (Pan)