The Interdependency series by John Scalzi has a female MC, and several other important female characters.

https://en.m.wikipedia.org/wiki/The_Collapsing_Empire

Mistborn might be a little YA for you, but the main character is a girl who grows to become a badass woman.

She’s not so much helpless, but she does need to mentored in the first book of the trilogy.

• A Wizard’s Guide to Defensive Baking, T Kingfisher. Technically YA, but still a brilliant book that doesn’t shy away from being real. If doesn’t feel YA. T Kingfisher has plenty of other options to choose from as well.
• Legends and Lattes, Baldree. On the lighter and simpler side, enjoyable characters and character development.
• Of Shadow and Sea, Will Wight. Multiple strong female protags and with MC being an assassin, there’s plenty of stabbing. Part of trilogy.
• The Hollow Places, T. Kingfisher. More on the horror side of fantasy. Continues to have lovable characters
• The Murderbot Diaries, Martha Wells. Hilarious, sometimes violent, sci Fi. I guess technically not a female protags?
• Gideon the Ninth, Tamsyn Muir. Sci Fi with fantasy feel. Plenty violent, mystery, great female protags and characters, can be difficult to follow but still thoroughly enjoyable.
• Iron Widow, Xiran Jay Zhao. Sci Fi alternate History China with mech warriors. Murder and power to stop girls from being sacrificed. Fun for the whole family.
• Rosemary and Rue, Seanan McGuire. Urban faerie fantasy and investigator noir book one. She has a couple of urban fantasy series you may be interested in.

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• Ninefox Gambit, Yoon Ha Lee. MilitarySpace Sci Fi with intriguing technology and cultural evolutions. Creative and artistic.

I strongly recommend A Practical Guide to Evil. Strong female MC, character growth and change, strong supporting case with their own ocassional POV chapters, and a fascinating world. Also, it is a web serial, so zero dollars to read it.

I also have to second the post that said Gideon the Ninth. I’d specifically point you to the audiobook, as it is one of only 2 books where the audiobook felt better than the paper one to me.

Putting it here because I don’t see it in the list:

Girl Genius by Kaja and Phil Foglio

Steam punk and she does get twitterpatted about some boys but the whole story is about her making her way in the world.

Not sure if you’ve already read Discworld but the Witch series fits a lot of your requirements. Maskerade would by my first for it’s hilarity.

I really liked Iron Widow. The female lead is one tough woman fighting in a super unjust world. It’s a sci-fi with mechs and the world building is interesting. The sequel just came out and I am really enjoying how the series is unfolding.

You’d probably enjoy City of Brass and it’s sequels. Extremely unique, well written, exciting, and lots of twists and turns.

It does follow a couple of conspiracies as a central plot point though. Adventure mixed with political thriller.

Parable of the Sower by Octavia Butler

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A few off the top of the dome:

Elizabeth Moon - Deed of Paksenarrion trilogy (military fantasy with light magic)

Louis McMaster Bujold - Paladin of Souls (I would read Curse of Chalion first but it has a male protag and not strictly necessary)

For sci-fi you should try some Becky Chambers. They are adult but dont have much action if that matters to you - very character driven dramas in space.

I really liked How to become the Dark Lord and die trying by Django Wexler.

Fantasy isekai with a female mc and some fresh twists.

Maaaaybe some stuff by Octavia E Butler? Many of her novels have famle MC’s. If you want some retro sci/fantasy, you could check out the Dragonflight books by Anne McCaffrey