My 2 cents, this is the same topic as your (I think) social media questions... there are so many positives and so many negatives..
If I don't know how to spell something, I'd rather be told I've totally balls'd it up by an app than perhaps make a mistake that may potentially be make or break depending on who reads it.. But I should recognise that shortcoming in my spelling ability and try and learn that word 'for next time'.... but if I become reliant on it and ignore the necessity for me to do some mental graft, then I am obviously becoming "dumber".
But, is there a place for it? Much like social media/arsebook, yes of course!! I've got friends who are dyslexic and really need the help and support of some software/apps.
That being said, as someone who needs to hire people in life, if there are apps making CVs for people, then the bar will shift and what may be currently smart, will suddenly be a poor path to take..
As a society, its become harder to kill yourself through complete idiocy...this worries me more than anything as historically that could spell the end of a certain set of genes....nowadays the idiocy (nature or nuture) lives on... This is far more concerning than general apps (imo).