Identity and auth provider consumers are a mix of lazy, under resourced, and unsophisticated. Lots of inertia and checkbox completion vs due diligence. It's also a pain to move, having had to help an enterprise move from Lastpass to 1password. Even worse trying to swap out idps. Operating your own idp internally requires sophistication and resources (engineering talent, org will, etc).

I am sympathetic to the idea of not reinforcing bad behavior at a vendor, but also mindful that sometimes you're going to risk accept and move on (and revisit when the contract is up for renewal). Time and resources are finite.

EDIT: With all the above said, Okta would not be my first idp choice, considering all available information.

(head of security @ fintech, I own customer and internal IAM, thoughts and opinions my own)