>>43758298its only unfeasible with Gamefreak because they're lazy. Even if you dont go all the way back to Kanto, 3 and 4 could have been connected. Or 4 and 5. Or 5 and 6. Or any gen areas they wanted. They could have made it so you can hop on a plane in Alola to go visit Unova in Ultra.
They just never bother. It's not like they can use limited space as an excuse, they just dont because people will buy regardless
