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I've wanted a game like Pokemon Legends for a while, but it sucks to see the last 20 odd years of games discredited so often when people talk about it. Arceus to me is just the logical ending of Pokemon's recent experiments. Mounts were a minimal feature in XY, which then became Soaring in ORAS, which then became Rides in SM before ultimately coming back for this game. Sneaking was another idea pitched on the 3DS with ORAS, and overworld encounters were added formally in Let's Go. SM got rid of traditional Gyms, and gave us boss monsters in Totems and Necrozma, which the Nobles are likely drawing inspiration from. Then all the recreational stuff like character creation and Pokemon interacting with the player outside of battles (Amie, Camps, Refresh, etc), which have been pretty consistent features.
I guess people want more radical departures with each release, but they've said in the past that they don't want to change the series too quickly. So we get these incremental changes over long time instead.