Did on-going feud between Mullally and Messing lead to show's cancellation ?
Apparently, there's been a feud going on between Megan Mullally and Debra Messing which the tabloids have been reporting about. Each actress has 'unfollowed' the other on social media the past six months or so, and each has left 'cryptic messages' on their own accounts (referring to the other actress). Mullally also missed two episodes for this season, and there's an assumption it may have to do with their feud.
It's speculated the dissolving of their friendship led to the network deciding to end this show.
https://www.cheatsheet.com/entertainment/will-grace-are-debra-messing-and-megan-mullally-really-feuding.html/
https://www.usmagazine.com/entertainment/news/megan-mullally-to-miss-will-grace-episodes-amid-feud-rumors/
https://radaronline.com/exclusives/2019/10/megan-mullally-ditches-will-grace-debra-messing-feud/
https://pagesix.com/2019/10/25/megan-mullally-takes-leave-from-will-grace-amid-debra-messing-feud-rumors/