@Riot Why there is only 1 female champion this year?

If you take the last 365 days, you get:

Kindred: Lamb female Illaoi: female Jhin: male Aurelion Sol: male Taliyah: female Kled: male (Skaarl is female)

Four champions were released this year (with a fifth coming).

That isn't exactly a big sample size.

illaoi and taliyah.

I don't remember any females ;D

Cough 2 Female Champs Cough

If you mean since January 1st, because those were the Champions that the design team was able to produce to a satisfactory quality to be released at this time. Let us not forget, there once was a gunslinger champion being deigned and even tested in game that has almost completely scrapped, and remade into Kindred and his model designed became a skin for Jhin.

It takes time to produce and release champions now, and sometimes they get delayed due to development issues (Azir), need to be put on ice due to lack of ideas/tech (Aurelion Sol), or scrapped entirely (Gunslinger).

Because of the patriarchy.