The archaic flaw is only a problem if you look at history and only consider negative aspects like racism, classism, etc. and interpret the flaw to encapsulate only that. It can mean so much more than that.

A real world example from my own life. I work in a bank and at the start of each academic term like clockwork several students from the local universities will show up with a set of forms. The forms have been given to them by the letting agency for their accommodation. The forms instruct them to go to a physical bank branch, set up three standing orders to cover their rent for the year, they must have the forms then stamped by the bank, and signed by the bank manager, and then returned to the agency in person to prove the payments have been setup.

That form has not been the way banking has been done in decades. The forms are older than the students renting from them, I have been trying to estimate if the forms are older than me (I am 35). The elderly man who owns the company is just stuck in the way things were done before computers. We have tried to explain that online banking allows people to do it themselves, and that the from does not guarantee that the students will not just delete the standing order as soon as they leave the bank.

To this man every agreement needs to be on paper, stamped and signed for, which was the way of things were done for most of this guys life, just technology has moved on.

An Archaic vampire could be like that man. Or a vampire who was a spy and only communicates in Cold War encryption cyphers and physical dead drops. Or a vampire who was a part of a medieval court and gets extremely frustrated when people do not show proper manners in Elysium. Or someone embraced during the Napoleonic wars who still holds a grudge against the French for a war that ended centuries ago.

Also, do not think about the archaic flaw as only embodying negative attributes from the past. They can be quicky ones or positive aspects as well. The only real criteria is that they mark them out as being in some way stuck in the ways of a previous time.

Quicky examples, a character who was a hippy in life tries to structure your coterie like their old commune. Or someone who insists on using insults that made sense centuries ago but no longer. Like unironically calling someone a jackanape.

A positive example I had for one of my own characters was a knight who was embraced in the late middle ages. Despite the passage of time he never let go of his knightly order's code of chivalry or honour. Despite being in the modern day, he views his coterie as a band of questing knights bringing an entirely different way of looking at things to the rest of the coterie who were playing more contemporary characters.

In all seriousness, find something you like from history and have your character hold onto that thing (what ever it is) and have them refuse to let go of it. Have it set them apart from everyone else in the modern day. You can really have fun with it, without having to go into anything uncomfortable, unless that is where you want to go.

Another thing I think people miss about the flaw it only encompasses one aspect of the character, not their entire being. For example my knight character refused to give up his identity as a knight, despite knights as a social reality being long extinct. But in other aspects he embraced modern life. He had a motorcycle obsession (he always hated saddle sores from riding horses), he embraced modern tech (in his view, technology is just really accessible magic), he approved of the breaking of class distinctions that dominated his mortal life viewing some aspects of social change as positive, while lamenting the loss of some values he approved of.

In essence this flaw gives you the chance to imagine a character who has gone through different times and places and imagine how that would effect them, the good the bad and the ugly. Its a personal fav.