Completely agree that growth mindset can be like a stick to bear people with who suffer under systemic level barriers. We're not Americans, believing that we are all temporarily embarrassed millionaires who just need to dream hard enough, after all.
I read OP as being about a general tendency among otherwise mainstream, not particularly traumatised or disadvantaged people to closed mindedness, jobsworthiness, or the other minor areas where people shoot down new possibilities because of their own discomfort with engaging with them. Of course we can't see what's beneath the surface and it may be that fear and anxiety are closer for these folk.
I'm interested in your point @mumof2oneofeach - my DH is very similar, super pragmatic and logical and needs 10 good reasons why an idea should be implemented. Quite often, it's because he has seen many potential glitches others have not. He is great in this way.
However - there is an emotional component, (which he would vehemently deny). His mother is a very "don't get excited, it might not ever happen" kind of person and this rubs off on him as caution; the status quo is always better than the new.
I am the opposite, very can-do. Sometimes I am frustrated; because often an idea needs acceptance, enthusiasm, then room to grow. It might change into a different idea under this scrutiny - but it may need this.
Ideas are usually the germs of visions of a better world. Even an idea like "hey, why don't we order the copier paper quarterly not monthly" has come from a human with a divine spark of wanting to solve a problem they've noticed. I think all ideas and idea-havers should be treasured. Ideas should be weighed up, sure, and often discarded almost immediately. But someone bringing an idea can tell if the hearer is thinking of their own fear in writing it off, or genuinely considering it.