Unless using your own dogfood prevents you from fixing it if it breaks
https://www.theguardian.com/technology/2021/oct/05/facebook-...
I have a memory that Slack fell into this trap too (I could be wrong)
Now I’m imagining the folks at Slack gritting their teeth and using MS Teams
Facebook notoriously had to cut open the doors to one of their data centers.
Google SRE still keeps IRC available in case of an emergency.