A qualified generalist ops admin should be productive on any modern UNIX or UNIX-like within a couple weeks.
Figuring out how the guy last year set up FreeBSD consists of similar effort and process as figuring out how the guy last year set up Debian or CentOS or SUSE.
It can be challenging. I basically bought my house based on figuring that out for people in the old days.
It’s not an issue with FreeBSD or anything per se. Usually there’s a genius superhero guy who does whatever, who burns out/quits/otherwise goes away, and the business is stuck.
Figuring out how the guy last year set up FreeBSD consists of similar effort and process as figuring out how the guy last year set up Debian or CentOS or SUSE.