Debian Stable might be more analogous to CentOS, but they don't do major feature backports like RHEL does, so I find stable is often much too old by the time it's actually released.
On the other hand, CentOS systems tend to last much longer due to the 10-year support cycle. So I often encounter wild specimens that are even older than Debian oldstable.
Right now, I've got a bunch of CentOS 6 servers with 2.6.32 kernels that are freshly out of support this month. I was hoping to replace them with 8, but now I'll probably have to settle for 7. At least I can take consolation in the fact that I haven't been called in to troubleshoot any CentOS 5 servers lately.
There is no real equivalent to CentOS Stream in Debian's release model.
Perhaps the closest is "the DAK upload queue for Debian stable", but that tends to contain mostly security updates, and according to other posts in this thread that is the one case where CentOS Stream is not an upstream of RHEL.
CentOS Stream contains feature backports, which generally don't happen in Debian stable, but it's only very specific backports, not every package gets updated like in Debian testing.
I'd put it like:
Fedora rawhide <=> Debian unstable
Fedora <=> Debian testing
CentOS Stream <=> DAK upload queue for Debian stable
The new CentOS "Stream" sounds like it will be more like Debian Testing.