Over the top? (seriously people stop making hard for us no native English users, and older too, with all this acronyms -.-' )
Nah. In the opening video the scene of a soldier that tranforms into a mindflier is more, way more, creepy and frightening we can see the fear of the soldier while he run for his life, the panic in his eyes when he start to become a mindflier in paragon the birth of Us the intellectual devourer is almost cute.
I dare to say that the intro made quite clear what to expect.
Furthermore the main character is the protagonist of the story, that means that they are not your average John/Jane easy to be startled or terrified, furthermore one way or anoher the main character are adventurers that reached level one in a specific class.
Not too well versed in DnD stuff, but i'm pretty sure a lvl 1 in a mindflayer ship might as well be a peasant.
I do agree with the sentiment, though. MC really doesn't feel like a young adventurer, which is pretty enjoyable, so it's easy for me to look past that aspect and just headcanon that the tadpole is tampering with my char's abilities.