[BSDobelix]

>but I'm concerned about my job now since I was in charge of this and it's been a disaster.

Your boss should understand this, if you are a medium sized company with highly configured boxes (pet style) and have to change major versions, crazy stuff always happens, I can tell you story's (especially firmware and blob related but also cronjobs, "optimized"-shell scripts, to really old php stuff and so on) about upgrades that will drive you to the church before you touch any "dnf upgrade", however that's why i tend for much shorter upgrade times (within 3-5 years).

Customer had highly customized RHEL7 boxes, upgrade to 8 was "terror inducing", and went so far to rebuild nearly the whole infra (about 20 boxes but with really excellent documentation). You are not alone.