I immediately think less of anyone who doesn’t know the difference between a noun and an adjective.
Calling someone ‘a’ Karen is using the word as an adjective.
Calling someone ‘Karen’ is using it as a proper noun.
I’m guessing you just looked at the upvoted comment that said it’s not an adjective and assumed it was correct.
For shame.
If I call you a Muppet does that make Muppet an adjective?
On the internet anyone and everyone is always right.
My brother in christ you need to retake primary school English and learn what nouns are
This is a person This is a human This is an individual
Are all of those adjectives? lol
In this context, ‘This’ is the adjective, as it describes the amount of Karens there are in this sentence. Karen is indeed the noun in this situation.
An example of using ‘Karen’ as an adjective would be: ‘did you how so-and-so went completely Karen on that clerk?’
You visualize how so-and-so acted in a particular way towards the clerk. The adjective to describe the behavior was ‘Karen’.
Hope that clears things up.