I think this is kind of a bad take. There have been plenty of "monster catching game"/"pokemon with the serial numbers filed off" games that have been somewhat successful, but no smash hits. "Cassette Beasts", "Nexomon" and "Temtem" spring to mind. From larger studios there has been stuff like "Monster Hunter Stories" and "World of Final Fantasy".

Palworld is really a "survival crafting" game and is closer to a game like "Conan Exiles" which has a similar gameplay mechanic of capturing slaves to put to work in your base.

What made Palworld stand out was the shock factor elements of "Pokemon with guns", "make pokemon work as slaves in a factory" and "grind up pokemon for meat", which streamers were able to convert into clickbait thumbnails and views.