Not to belabor this sideline, but the dragon was by far the worst at our table as well.
We had two players and the DM, all with zero D&D experience, plus two somewhat experienced players. (The DM thought that being a PC to get experience first sounded like no fun.) DM figured the module had to be "right" and didn't realize that the breath weapon was guaranteed to straight-up kill a PC with no death saves... Which happened, except we eventually (after a big rules argument and explanation) retconned it to be only enough damage to knock unconscious. After that, we had no clue how to progress, given that we had no real ranged attackers.
It was stressful and everybody was angry.
By comparison, the thread headline encounter was unfair, but at least it was clear that pop-up healing would be an option afterward, and it happened after the dragon train wreck, so we were already prepared for things to be unfair.
(Thankfully, we stuck with it and enjoyed much of the later stuff, and eventually finished the whole module and decided not to continue to the second half.)