I'd pick up FreeBSD in a heartbeat if I knew that the investment in learning the platform would help me be productive in production. But like you said, it's not 1994 anymore and modern deployment and maintenance of an application stack is docker and k8s. A trend where the OS is abstracted away as much as possible. So why invest in FreeBSD? Okay, so maybe it's a nice OS for appliances; though so is Linux and I can continue to leverage my knowledge.
At home I run an appliance and thought I'd deploy FreeBSD on it to run my storage server. I was really excited to deploy ZFS, the BSD killer app. The justification for this getting more difficult to make since ZFS on Linux is production ready.
I want to use FreeBSD. I don't care that it's not mainstream. The unfortunate issue is that it's falling behind in my use-case, by a lot and that's a bummer.