It's not that she has to announce or deal with bad news or "tough" questions or even constantly lie, it's that she's so bad and unprepared for her job. At Jen Psaki was well trained and qualified for this job, even if Jen Psaki just read pre-scripted notes, she was well rehearsed. Karine Jean-Pierre is like a "deer in the headlights" day after day, completely unprepared, sloppy answers, etc.
Consider Kayleigh McEnany as a "gold" standard. You never caught her off-guard at any moment. She was always well prepared for any question and could give a clear, succinct answer.