I've been building network controllers my entire career and the "hard part" has never been interacting with devices. Like who cares if you're using Ansible? The hard part is configuring these things; Every vendor has a different way of configuring the same 5 solutions to the same problem, and even with a single vendor network you may have to tailor your configs based on the device type that you're configuring.

IMO there needs to be some higher level abstractions emerge. Half the time I just need a layer 2 network (please don't ask me to configure it one way for a point-to-point vs greater than two endpoints. if there's an optimization to be made do it for me). The other half the time I need a layer 3 network that can peer with BGP (don't ask me what underlay or overlay protocols to use, I only care about the VLANs I'm terminating on).

Slightly related: Cloud providers expose APIs for networks to setup peerings between the cloud provider's network and the network's end customers. These APIs aren't standardized at all, and are a complete PITA for networks that try to integrate their SDN solution with multiple cloud providers. This is one area of complexity that the big guys could cleanup without a lot of work.