6. Ilithid checks - I look at this question from the perspective of the subsequent game plot.
There will indeed be stronger ones, for example, the three sons of God, they should be given a certain value of resistance to Ilithid checks, so that the plot is reasonable.
Maybe it's just because the enemies we are facing are too weak (Lv1~Lv5)
It is necessary for the enemies of Lv9 ~ Lv 12 to give Ilithid checks considerable resistance, and also encourage players to use more Ilithid power to develop to different endings.
Do you still fail 0 DC illithid wisdom checks if you roll a 1? You used to, but I've not done it for a while so not sure if that has been fixed. In general, and unlike some others, I don't mind critical fails on skill checks but that does seem ridiculous. At least call it DC 2 if you want it to be possible to fail the check!
That aside, I do agree that we might find more difficult illithid wisdom checks later in the game, but I also think that the game should make it that we automatically pass any DC 0 checks without rolling. If there's a zero chance of failing then it's just boring time-wasting, whereas it's just counterintuitive that if the check doesn't involve any difficulty that it can be failed!