I am an old person. As a child, I remember going in to a store called "The Early Learning Centre". In the window there was a large wooden train set that children could play with. It was exactly the same as the set in this game. My 6yr old son now plays this game, and he has a set of real wooden tracks too. So when he plays with his real one and his imagination requires more than the pieces he has, then he plays this game and builds what he otherwise couldn't have built. Fore example; the IRL set doesn't have rivers, and you can't get it the train and experience your new track in first person. Thank you very much for making an adult an a small child very happy at the same time.
What is the game? Make your own train set. Either complete objectives by making a track, sort of like a puzzle game. Or you can go full sandbox and make a lovely town.

Wooden train set, perfect nostalgia

Good sandbox train game with good graphics and mechanics