I gave this film a 7.2, I liked it, it lacked some stuff but still a fun 83 minute ride that I would probably rewatch.
In this review I'm going to compare it to Ghibli movies a lot, because I believe pretty much its entire identity is influenced by them and this is the best way to analyze, I'm going to talk about the shortcomings and the triumphs of this movie the best I can, hope you enjoy!

Ponoc & Ghibli, The visuals of Mary and the Witch's Flower

For those of you who don't know, Hiromasa Yonebayashi (this movie's writer and director) has worked as an animator in studio Ghibli since Princess Mononoke, first as an in-between animator and then as a key animator and director, and that's the main reason his post-Ghibli works look so much like Ghibli films, in terms of animation and visual aesthetics (check out Modest Heroes), a lot of the visual ideas and choices made in those films were probably his and after leaving that studio he makes a movie that I believe, looks as good as the most visually stunning Ghibli films (Howl's Moving Castle and Spirited Away).

Remember this girl? she was in Kiki's Delivery Service, only in one scene, she has the same hair as Mary and has a cat identical to Tib (Mary's cat). This was Yonebayashi's first movie after leaving Ghibli after many years and it seems like he's taking a ton of ideas with him. Perhaps to establish his territory and say that even though he's left that studio behind it's not like he's left all those years of experience behind and he's going to put all his knowledge from Ghibli to good use in his new studio.

There are numerous parallels to other Ghibli movies in this film, here's some that caught my eyes:

Howl's Moving Castle:

Spirited Away:

And of course Kiki's Delivery Service:

Hell, even the opening logo looks like Ghibli's:

Why copy? you have what it takes, you can totally pull it off, why not bring your own ideas to the table? this was kind of a petty move if I'm being honest, but I understand where he's coming from, when Hiromasa Yonebayashi screened the film for his former colleagues at Studio Ghibli, Hayao Miyazaki congratulated him but said he wouldn't see the film ( Source: https://www.imdb.com/title/tt6336356/trivia?item=tr3463361 ), I can perfectly imagine why he left that studio and why he brought so many ideas with him, Hayao Miyazaki has a long history of controlling and getting in the way of his directors that you can look up for yourself.

All of that aside, I do consider Mary and the Witch's Flower to be one of the best looking anime films ever made, both in terms of cinematography and animation this movie is phenomenal, and I'm not sure how else to put this without repeating myself over and over again, so just watch the movie and see for yourself.
I feel like with this film he wanted to flex and show off just how well he understands the craft and how better off he is without Ghibli, and I wish I could say the same thing for the story.

Story

While it isn't exactly bad, it could've been much better.
A girl thrust into a new wondrous world who gets caught up in all kinds of situations, a recurring theme in Ghibli films such as Spirited Away, The Cat Returns, Kiki's delivery Service and My Neighbor Totoro.
But unlike all of those movies, the characters in this film don't really have any depth to them or go through any development, I would have loved to see Mary go from being a child who hates herself to someone mature who can accept herself for who she is, like Anna in When Marnie Was There (which ironically enough, was made by the same creator), but nothing like that happens, her primary state isn't even that emphasized, she says she wants to change in just one scene and she's sick of her frizzy hair, there's not even any room for development, at the end of the day this movie is just about a girl who gets caught up in some magical stuff and that's it.

And the side character Peter, we don't really get to know him that much, giving him a little more personality would have raised the stakes in the plot points that he was a part of, if he had a more meaningful connection with Mary, then her trying to save him would have been more intense and her triumph at the end would have been more satisfying.

The antagonists are just generic, ESPECIALLY compared to the usual antagonists you get from Ghibli.
One of the things that really sets Ghibli aside from any other studio for me in terms of storytelling, is that in a Ghibli film there's no pure malice, not really (Tales From Earthsea aside, fuck that movie), Princess Mononoke and Nausicaä of the Valley of the Wind are perfect examples, Lady Eboshi (from Princess Mononoke) rescued all of those women from brothels and helped treat many sick people, same with Kushana (Nausicaä of the Valley of the Wind), they're not just brainless villains like characters you get in Disney films, they have a personality and feel like actual people with clashing ideologies, that's why I don't get why people keep comparing Ghibli to Disney and saying Hayao Miyazaki is the Walt Disney of Japan.
But in Mary and the Witch's Flower the antagonists are scientists who are too dumb to predict their plan won't end well.

Final words

Did I compare it to Ghibli too much? When you look at this movie as its own thing (which is exactly what one should do! don't mind my rambling) the story isn't half bad, it feels magical at some points, I was actually feeling kind of broken inside when it ended, but I can't help but ruin my enjoyment.

Thanks for reading my review, and now, the score:
Eeny, Meeny, Miny, Moe... 72

If you have anything to say, perhaps to critique my critique leave a private message (or a public one) for me and I'll definitely get back to you!