Not if it's done well. A bit of lore and interesting quests can save this very easily. Also, why would airships be pointless in such a massive world? Even with a large world it's not like you can't block off certain areas via lakes, oceans, mountains etc.
Fun fact: You actually can't climb mountains in a lot of open world games. Crazy I know.
A lot of rpgs have optional towns and dungeons, hell, even FFXII had them and they were great.