This is how moving from town to town will look like in the game if stripped of the art and UI:

I thought that it would an easy thing to implement. Almost the same algorithm worked in Chip ’n Dale Rescue Rangers in 1990.

And that was so long ago, shouldn’t the progress in the game industry help with such “classic” tasks? Of course, it helps, it’s just not a “make it fast and make it good” button. Some things, like saving data to persistent storage or marking cleared stages/towns will take time no matter what engine is used.