So I'm 20 hours into Shield now and it's clear this just is a bad argument. There's lots in this game that wouldn't be possible on a 3DS and plenty of things that push the gameplay forward beyond "big pokemon". My favorites are the new gym concept with challenges, the wild area and the ability to challenge yourself with over leveled pokemon right away, the camping mechanic giving your team a HP/PP/EXP boost based on interactions and the curry mini game, less load times and larger areas, and more.
If the bar was "Breath of the Wild but Pokemon" then yes, this doesn't hit it. But as someone who's playing the game it's very much a big leap forward for the franchise.