I am not a Centurion card holder. I did reach out to the Centurion staff last fall (2018) that I have known since 2014 (that year I breached the required threshold 200,000 but didn't get an invite). They also say the program is closed with no invites being sent out in 2018. I told her if they need a quota in 2019 send me an invite because I now charge only to maximize value (ie no more 200,000 on a single card) over various brands of cards. That time I was switching my personal Plat card to Business Plat for the welcome bonus without having to change the "membership since" date.

If Centurion staff is reporting correctly saying there won't be any invitations for 2019 as well (ie two consecutive years of no invitations), then it's possible they reached max capacity and doesn't need to grow anymore. I think invitations and approvals gets loose when there is a recession - that's when AMEX need the profits and more willing to dilute existing users.