Take this with a grain of salt, but I thought the same thing (although in my case I'm talking romantasy (or a fantasy romance) back in the day when fantasy romance wasn't a thing. I spent a lot of time thinking about how swear words and slang would play out (in the context of my world), avoiding the overdone ones (you know, references to the "goddess" or "gods" or weird words that start with "z" and stuff like that. And I kept things that seem to be universal across a few centuries (like damn), and looked at the time period my fantasy was based on (many fantasies fit within a broader grouping like medieval-esque , pioneer-esque, renaissance-esque etc) and how they handled it during that time period. Then...yeah, I got it wrong and picked words that I still think work and fit, but taken out of context (these are not bad words intrinsically) people didn't like them and gave me a lot of one star reviews for "how I referenced things" So why do people use "fuck and shit" and words like that to signify swearing? In my opinion it's like putting a palm tree on the cover of a book about Hawaii. There might not be a palm tree in the story, but it "signifies" Hawaii to people looking for a story about Hawaii, in the same way "fuck" is a swear word pretty much across the board, and it's understood to be a swear word so it fades into the background (you know how some people in real life use it as an exclmation point or just punctuation in their dialogue?) and it really isn't visible anymore than "and" or the" or using "said" as a dialog tag. You can use anything you want and think would work for your story, "but" there are always going to be literal readers or readers who don't understand, or just don't like what you pick. And like the saying goes, "is this the hill you want to die on?" If it's important to your characterisation, I'd say go for it. I mean, it'd add to a character if he has a unique way of swearing, or if it illuminates your world in some way, but if it's just to address an opportunity you might want to consider (and I am not trying to be rude here, but just asking a genuine question) if this is something important to your story or important to you.
