I think you need to study patents and patenting. "The first Pokémon-related patent in the United States was issued to Nintendo and Game Freak on June 26th, 2001. (I took that verbatim from a google search). Nintendo did file and renew the patent that was granted to them both in the United States and Japan. Now if Palworld developers had the money and knew of this that Nintendo hadn't yet renewed the patents or whatever, they should've pounced on it. But they didn't, they proceeded to develop the game and then release it while Nintendo renewed the patents which in turn, lead to the patent lawsuit.
And I doubt that Palworld too checked in with Nintendo/Game Freak. So you see, if you patent an idea, a mechanic .etc then too bad for others. They either work with you, a group or individual who filed the patent for a deal or they can just punch sand lest they risk patent lawsuits coming your way.