New Pokemon Snap game only sold 2.1 million copies worldwide. The main games have sold over 22 million. The game is super niche. I think that's part of the issue. From May to August, it only increased it sales .06 million. It hasn't even outsold the original from N64 yet (3.63 Million).
Additionally, let's look at it from an outside perspective, the ride concept is you take pictures of Pokemon and then what? If you tell people to buy pictures of AAs that don't even include the people taking them, its going to be a weird and hard sell and look 100% like a cash grab.
Universal can't go simple with the main Pokemon attraction being too simplistic. Pokemon fans have one of the largest demographic spreads so any ride or attraction will still need that power aspect to appease adults fans/more thrill seeking fans to a level.