I think that poor opsec is usually either a symptom of naivety from older people who don't know any better, think the Clinton E-mail server/password debacle, or younger people who never grew up being taught that "stranger-danger" was a thing on the internet. If you're of a certain age, you almost certainly remember growing up and being taught that you never share your personal information on the internet, lest some scary boogeyman will come and kidnap you, kill your grandma, and steal your dog. To me, seeing the rapid change in how people have just willingly forked over personal information in the past ~15 years has been bewildering. In less than a generation, we went from "Don't tell ANYONE your real name online or you will die in your sleep!" to "LMAO, give us your D.O.B, blood type, and SSN to find out what Harry Potter character you are!". It's sheer lunacy. Social media is definitely the main culprit, but society as a whole seems to have trended in the direction of eschewing privacy away as a trivial subject. With everyone having a cellphone and social media, people are expected to be reachable at all times, and (((The Media

))) definitely helps the narrative by portraying people who object to this shit as outliers, some sort of "-theorist", or crazy, and coming up with snarky names or catchphrases when people don't go along with it.
The best defence against doxing is not to do things that make people want to dox you.
I would have to disagree there. Even being a member of KF without even posting could be a social death-knell for some people if found out. Today's hero is tomorrow's mortal enemy. And everything throughout history is judged by the lens of "Current Year

" Look at the degenerate troob mob, and how they turned on their patron saint of Woke, JKR, the MINUTE that she merely suggested that biological woman might actually be a thing. The amount of hate, fury, vitriol, death threats, and doxxing she has put up with for YEARS at this point is insane. Or look at the busybody people who have nothing better to do in their pathetic lives that dig up 10-20 year old forum posts, tweets, blog posts, or videos now deemed "pRoBlEmAtIc" and attempt to destroy people's lives in order to give themselves a pat on the back or for social media clout. Today's "what's up, bro?" is tomorrow's "Nigger faggot".
Its not hard to practice good opsec online. Keep separate passwords for all of your important shit. Don't share overly personal information, especially on the KF. If you post pictures or other media, scrub all potential identifying information and metadata. Like the title says, don't be retarded and reuse the same username in multiple places, keep things simple and intentionally vague, I may or may not be a "Smarmy Jew"

. Just about everyone has an online thumbprint whether they are aware of it or not, and the most basic of info is readily accessible for many people, so the point is to keep that as separate from your alternate online activity(ies) as possible.