It might be time for them to try out Unity or Unreal engine for switch games. Pokemon's inhouse engine doesn't seem to be doing that great.

I think even Pokemon Arceus had a difficult development as well. The original in house engine was replaced with a modified version of Zelda's Breath of the Wild engine.

I know Mario kart tour was written in unity I think, and it works well across my families wide range of devices.

Edit: It seems some pokemon remakes were done with unity too: https://exputer.com/news/nintendo/pokemon-brilliant-diamond-...