DISCO showed these people aren't professionals because of the amount of times they have their meltdowns during an emergency with lives on the line under a ticking clock.
Having a breakdown is fine... but not during a crisis. That can cost lives. For example, if a doctor in an ER had a group of patients all in critical condition, and that doctor was losing it while those people are dying, you think he should be taken seriously?
That's why they are called professionals...you handle the job at hand and have your emotional breakdown on your own time. Doctors, soldiers, cops, firefighters, etc... they all go through a lot of training to BE professionals. Some can't cut it, and wash out. Others, those breakdowns happen, and they get fired... precisely because it puts OTHER LIVES at risk.
TOS - ENT, I can actually take those Starfleet officers seriously. DISCO? Don't make me laugh.