The problem is that you make it sound as conscious change, and that is simply not true.
But... it is a factor. Not the only factor, but definitely one of the large ones. Even in cases where it doesn't involve "PC" speak eg. trying to appear more prestigious, polite or professional. This trickles down to common vernacular.
Why do you think people started saying "heck" instead of "hell" and is commonplace in the likes of the US even to this day? It was a conscious decision, and still is. People decided "hell" was a bit offensive and changed it as such - ironically this came from conservative christians!
You claim people have no decision or say in changing language, when in fact they do it all the time.
People have a say in how they use language but not how others use it. Having said that, if enough people do the same thing, change can happen. My point in this thread remains that it's not as easy as saying "let's reclaim the use of the word 'man'".
I agree with you re the word "heck", of course, but I'd still say that changing a language is, by and large, not a conscious process. If religion hadn't been such a big factor in everyday lives, heck probably wouldn't be in use at all. Context matters.
BTW, I found this when googling "heck etymology":
https://dictionaryblog.cambridge.org/2012/08/14/gosh-darn-it-to-heck/
