I Want It (ほしい)

ほしい takes が for the thing wanted, the same pattern たい runs on. Neither borrows を, even though English “want” would normally take a direct object. Both wants describe a state you’re in, not an action you’re doing to the object.

Talking about someone else’s want swaps ほしい for 欲しがっている, the exact same shift たい makes into たがっている. Notice the particle changes too, 欲しがる takes を like a normal verb, while plain ほしい takes が like an adjective. The whole word class changes, not just the ending.