Can “radgie gadgie” be used for an old man who is angry at grown-up's misdemeanor?

Recently I found a word, “radgie gadgie” in an old post in EL&U by Brian Hooper (September 13, 2012), asking the origin of “They don’t know they’re born,” that began with the paragraph; “Practicing today for my forthcoming role as radgie gadgie, I was having a little rant about modern youth; “They don’t know they’re born.”

As I was unfamiliar with the word, “radgie gadgie,” I checked its meaning on online dictionaries. I failed to check it both in Oxford and Cambridge dictionaries, but got definitions in two sources;

Radgie gadgie: A bad-tempered old man. - Wikitionary

Radgie gadgie: An angry person, typically an old man, most often angry at the shenanigans of children and teenagers. - urban dictionary

Though “radgie gadgie” applies to any angry old man in Wikitionary, but it refers to an old man who is particularly angry at children's or teens’ misdemeanors.

Is it improper to use “radgie gadgie” to an old man who is angry with grown-up’s breach of etiquette or misdemeanor, such as littering trash in the street, manspreading in the bus, and cutting into the waiting line at the service counter? If it is, what is the alternative expression that applies to the old man who is angry at a neighboring adult's uncivil behaviour?

Radgie gadgie is described as Geordie by Wiktionary and Geordie is, according to Wikipedia, Geordie

Geordie (/ˈdʒɔːrdi/) is a nickname for a person from the Tyneside area of North East England,[1] and the dialect used by its inhabitants. The term is also used to refer to anyone from North East England. (emphasis added.)

This explains why I have never heard or read the term.

As a slang word in a local dialect, the overriding question is: Do you want people to understand you? Perhaps this term is widely understood in England, but I doubt it. Someone expert in British English as she is spoken today should weigh in on that.

Now I will really venture into opinion. Using a slang term from a society of which one is not a member risks using it inappropriately and/or being found faintly (or not-so-faintly) ridiculous, especially if one is not in one's youth. (Dear OP, we run the risk of being found ridiculous by the young alien hip no matter what we do.) So my advice is to not use this term or use it only among people with whom you have a solid rapport.

I suggest curmudgeon as an alternative. According to Merriam-Webster, a curmudgeon is:

a crusty, ill-tempered, and usually old man

This is an old-fashioned word, but much more in the mainstream than radgie gadgie, and well represented in literature.

MW gives as an example sentence:

We were in Edinburgh visiting the in-laws. I was, as usual, being a grumpy old curmudgeon. My people don't travel well.

— David Mamet, Jafsie and John Henry Essays

and

But his views on the tech industry are those of a curmudgeon.

— Alexander Zaitchik, The New Republic, "Is Josh Hawley For Real?," 25 July 2019