It will show a different perspective even to the well-known stories.
Anime has been around for more than half a century, and like any medium that has stayed alive long enough, it has started to repeat itself. A few ways may help the authors spice up the tried and true tropes: deconstruction of the genre that quite often goes along with self-mockery (isekai, we're looking at you), careful mixing of genres, different takes on the same plots, and many others. Long gone are the days of the dominance of the typical high schooler as a lead character: modern protagonists are quite diverse, but among them there are still not so many girls, which is a shame.
The number of titles with a female protagonist in the past ten years is not high. You may remember Made in Abyss, Bocchi the Rock, Violet Evergarden, Wotakoi, Stone Ocean, The Promised Neverland, and maybe sprinkle a few more titles from the more obscure genres. Compared to the hundreds of series that have been released in this time frame, it's nothing. If you look at the anime before that, you'd see many more female characters being the powertrains of the stories, so this is a recent development.
But what can a female lead offer? It's a unique perspective. Imagine watching Jujutsu Kaisen through Maki's eyes, or witnessing the events of Attack on Titans from Mikasa's point of view. Sounds interesting, right? A more in-depth look at how the Jujutsu world works instead of an outsider's perspective, a lot of self-flagellation that comes with being powerless, and a lot of training to overcome it... Maki makes a perfect shounen protagonist. Mikasa fits the template even better — and despite all that, they would offer something new to the genres that right now are nearly stagnating and trying to dig out some interesting ways to present the plot.
Also, that would help anime appeal to a broader demographic, make some genres more interesting to the female audience, and show the audience that any person can become a protagonist. The compassion mixed with apparent cold-heartedness that Akane from Psycho-Pass shows; the existential questions and wonderful humor that Motoko from Ghost in the Shell offers; the frustration and anger that Ryuko from Kill la Kill emanates; and many more things, many more cocktails of complex emotions that we cannot see in the regular male protagonist can be explored through the female leads.
Some stories really can get another layer of depth and complexity if you swap the boy for the girl. And some stories definitely should.