I agree that that's what the main games are for, but I also think that there's more than enough room in Pokemon's franchise for side games that cater to older fans with more complex battle and sim mechanics. Pokemon Colosseum 1 & 2 feel like they could have been the starting point to a whole secondary line of JRPGs in the Pokemon world with unique stories and mechanics, but they never followed up on them and now those games are just a weird outlier in the franchise's history.