The problem is because it was an exact clone of RHEL, it's somewhere between difficult and impossible to have a proper community around it. Like I said it kind of revolved around "file a bug to Red Hat, wait for someone to pick it up, and then wait more for it to be shipped, which will be months away at best and could be years if it's not a paying customer's priority"
What I've seen people use CentOS for is testing a product intended to run on RHEL. For that, CentOS didn't need a separate community, and bugfixing at a pace different from RHEL would have been actively undesirable.
As far as I understand, you still need to connect to the Red Hat license server, and you're limited to 16 machines. That's just stupidly unsuitable for a CI worker pool of hundreds of VMs being created from scratch for every run.
If you do pay for RHEL you can have free non production subscriptions. Of course it's probably suspicious to pay for 1 production and 20000 testing servers, but it's pretty good if you are too small to negotiate an unlimited-machine subscription and you want to use RHEL in production.
It was never quite that, but that was the theory.
The problem is because it was an exact clone of RHEL, it's somewhere between difficult and impossible to have a proper community around it. Like I said it kind of revolved around "file a bug to Red Hat, wait for someone to pick it up, and then wait more for it to be shipped, which will be months away at best and could be years if it's not a paying customer's priority"