A few years back, in November 2020, Bungie decided to vault all of the DLC before their most recent at the time (Shadowkeep); this was to both keep the game fresh and without cheesy weapons and whatnot, as well as to keep the game size lower. The thing is, those campaigns and raids that they vaulted? Those were the only Free-to-play aspects aside from the basic game modes at the time.
What I'm getting at here though is that because they got rid of those experiences, a lot of the story elements that were previously established with those campaigns were gone. Now the only way to experience them is to:
a) Look at the in-game Timeline
b) read the lore books in their tab, or
c) watch YouTube for a good 2 hours at least to figure out what the hell the Fallen are, why the Witness is our Big Bad, and why Taniks always comes back.
Wowie! A wireless bat!