There is of course merit in everyone doing critical thinking, certainly. I don't think one obviates the other.
I do think having someone who is culturally allowed to put on the breaks and/or seek clarification about potential bad ideas is also worthwhile, for a couple of reasons I can see right off the bat:
1. It may reduce the 'bystander effect'[1].
2. It may reduce the negative emotional impact of naysaying a popular idea from inside the group that delivers it (subconscious social pressure impact).
The role could of course be abused and become yet another abusive fiefdom, but I think that just makes choosing the right person for the role more important.
I do think having someone who is culturally allowed to put on the breaks and/or seek clarification about potential bad ideas is also worthwhile, for a couple of reasons I can see right off the bat:
1. It may reduce the 'bystander effect'[1].
2. It may reduce the negative emotional impact of naysaying a popular idea from inside the group that delivers it (subconscious social pressure impact).
The role could of course be abused and become yet another abusive fiefdom, but I think that just makes choosing the right person for the role more important.
[1]: https://en.wikipedia.org/wiki/Bystander_effect#Taking_respon...