In just a few words, sexist and poorly written.
There are multiple problems with this movie, some of which like CGI are just personal preference. What isn't just preference though, is the bad writing around Wanda and how anti-progressive this movie is.
Spoilers ahead but,
Wanda as the main villain is a huge step back. While a show like WandaVision dived into the deep complexity of women as people and how people deal with grief, Doctor Strange 2 shows women as creatures suffering from "female hysteria" who cannot be reasoned with. Not only does this go against her character and her whole story in WandaVision, it is just bad representation and doesn't accurately portray women. This writing was bad representation even at the time the comic version came out in the 2000's, receiving fan backlash.
Besides Wanda, it is worth mentioning the LGBT representation which is two lesbian characters who are only seen in a flashback. While including represntation can be positive, this wasn't. It was the easiest and most ineffectual way to represent an entire group of people. No character was given to the two women, they were just story props and there are still no main characters in Marvel who are confirmed queer.It really felt like these women were tokens to the movie, not people.
Lastly, the writing was just awful. The heroes win by telling each other to "believe in themself." Much of the story focuses on a romance they just expect us to be invested in (I wasn't) and the climax literally has lines like "Uh huh" (one character says sassily taking the advtange in the fight). To which the scarlet witch says "nuh uh" (denying the sass). Like wow, great lines. I will quote them forever (no lines in this were quotable, all the lines were like this for me).