Why ansible? It's the best tool I know of for configuring systems when tyou can't build a premade image. I've tried puppet and chef but really like not needing any agent on the target system despite the pain of YAML syntax.
Because it's trash. It's sad. It's a slow, unreliable mishmash of suck that I loathe to work with.
Not needing an agent?!? You write "caching shit so we can run our remediation in under a century and one pass" funny. I build new machines in 3-4 minutes with a full remediation and like 300 data points to check with the good tools. But it takes tower 3-4 min to net started before actually doing anything, and then another few minutes for ~30 datapoints. I do NOT want to see it with an actual payload.
The only thing going for Ansible is the network effect of "everybody using it" and especially not learning well enough about anything else.
Everything has its quirks. It's quite hard to manage secrets in Nix without dropping them to nix store. Sops-nix is probably closest to ansible-vault, but I've yet to see some good solution for short lived secrets. (For example secrets that are only needed to deploy something but not to run it)
Nixos is great, but unfortunately I can't use it at work. I have migrated my home server infra to it though and plan to migrate my desktop the next time I have a free evening.