Multiple studies on the matter over the years have shown that people who curse regularly (n.b. not constantly, but regularly) actually tend to have a far more considerable vocabulary than those who do not. The old chestnut that people who curse have a poor command of language is actually nothing but a myth.
Additionally: "politically correct" was always meant to be an inherently disparaging term to refer to being considerate to others that may not share one's social position, ability, ethnicity, or any other social label. There is a greater emphasis on sensitivity with regards to diversity, and I'll grant you that some of it is transparently self-serving or simply using it as a means to an end. However, being less insensitive and immature is progress, not the opposite, and in any case it's only in small part relevant to the discussion of strong language.
There's a difference, too, between cursing and epithets. If someone is a bigot and hurls an epithet at someone, that's not really the same as someone calling another person an asshole, or saying dammit when they're unable to hack the mainframe (so to speak) -- similarly, it tends to be in the way that one uses language as to whether or not the cursing is effective. Usually strong language is at its best when it feels organic. I don't use a lot of strong language in most of my work, but I wouldn't avoid cursing since usually the only people who make a big deal over it are basically children anyway, and my works are most certainly not for that young an audience.
Using things like darn, gosh, and so forth can be appropriate for certain characters sometimes, but overall people don't tend to talk like that. It's one of the reasons why "shucks" is one of my favorite utterances ever, because I find it hilarious and uncommon.
There's a trend in some places, and one I am vehemently opposed to especially on the internet, to try and dumb everything down to "kid-friendly" levels. Plainly put: no. But realistically speaking, young people are around strong language all the time. They always have been. Censoring yourself, pretending this language doesn't exist, and trying to avoid certain words can all become very conspicuous and artificial. If words get in the way of expression, that's one thing; if they are organically part of a story, a character, or anything else, why try to hold yourself back? It just takes one click to mark a page as "nsfw" if people are that potentially bothered.
