“Basic” is often used in this sense to refer to someone “uninteresting,” “uncool,” or “from a lower class.”
It is often paired with the word “so” to form the phrase “so basic.”
This is a demeaning or derogatory term that refers to someone the speaker feels they are “superior to,” “above,” or “better than.”
An example in a sentence would be: “Don’t hang out with her: she’s so basic.”
“So basic” was popularized by the Netflix series Inventing Anna, about real-life con artist, Anna Sorokina, who pretended to be a German heiress in attempt to swindle banks out of large money and luxury hotels out of free rooms and services. “So basic” was also featured on a Saturday Night Live skit.
As the Netlix series debuted in 2022, this is a newly popularized term and may be heard more from a younger crowd. It is not as though this term were invented by Anna Sorokina or the Netflix series, so it may not always be a direct reference to that series.