I don't think that's been the case for a long, long time. Almost every new game on modern consoles and PCs will see one (or many) updates in its lifetime. Game cartridges, things we used to think of as immutable, are merely storage devices for delivery of the original game code. Two recent games I purchased for the Nintendo Switch, on cartridge, both required a download before I could play them.

It's more blurry but Games are still DONE in a way that an ongoing project where new features are constantly being added aren't. There are some exceptions like Minecraft but on average most games can not economically justify multiple full time engineers working on them for over a decade.

There is also the side issue of game engines which many teams reuse from game to game so maybe that doesn't really apply.

Terraria has been getting updates for 8 years now. Maybe that's why it's such a mess.