It's not hard to beat Prophet by >20%. As the paper itself states, it's designed for rapidly producing good enough forecasts at scale by domain experts with no stats background. If you have a small team consisting of domain experts, engineers and data science/statisticians, you should be able to build something which handily beats Prophet. If you're careful, you should be able to design a pipeline which can do the model tuning and selection in something resembling an "automated" manner (but it requires extreme care, and Prophet can't save you from the dangers herein either).
Prophet has a relatively narrow use case where it makes sense; not coincidentally, it makes sense at a place like Facebook where the sheer variety of problems to be tackled cannot scale to such a foregoing team for each such problem.
Prophet has received a lot of backlash for workflows it never intended, nor claimed, to be able to tackle. That's undeserved in my opinion. Zillow didn't lose money because it used Prophet, for example. But it still really shouldn't be used as a benchmark like this.