Was Planescape or Spelljammer or Dragonlance a "big adventure?"
Dragonlance, yes, the other two, no. Not every release is a big adventure book, that was true then just as much as it is now...
2014: Hoard of the Dragon Queen, Rise of Tiamat
2015: Princes of the Apocalypse, Out of the Abyss
2016: Curse of Strahd, Storm King’s Thunder
2017: Tomb of Annihilation
2018: Dungeon of the Mad Mage
2019: Descent into Avernus
2020: Rime of the Frostmaiden
2021: The Wild Beyond the Witchlight
2022: Shadow of the Dragon Queen
2023: Tyranny of Dragons, The Shattered Obelisk
2024: Vecna Eve of Ruin
2025: nothing
2026: nothing that so far was announced
It's really not that hard...