https://www.reddit.com/r/oneplus/comments/5k8ppv/former_cyan...
Not really a brilliant source, but I'd be inclined to believe it in this case. It fits with my understanding of the situation.
I used to use CM on everything but over the last few years I've been plenty happy with pure stock Android (+ root). Didn't end up using most of CM's extra features and found that it was often unstable and/or leaving lots of things just sort of half-working.
I personally stay away from there.
For root level access, I'd prefer relying on a project with actual reputation on the line, and has periodic spot checks.
Even CM's support for a wide range of hardware was mostly bankrolled by Cyanogen Inc, which will now no longer be funding them as they rebrand under LineageOS. It's unclear whether any but the most popular phones will continue to see support from a group that has "actual reputation" on the line or not.
They were the base Mod behind others (like Open Kang)
Privacy guard still beats whatever stock rom has.
The newer phones come with Oxygen OS or w/e they call it now and at least get some sort of periodic update.