https://www.polygon.com/2017/12/6/16743276/destiny-2-curse-of-osiris-content-locked-prestige-nightfall-raid

Destiny 2 players are up in arms yet again, now that the game’s first expansion, Curse of Osiris, has been released: People who have not purchased the add-on are discovering that they can no longer play some of the game’s high-level endgame content.

Endgame content in Destiny focuses on raids and the Nightfall strike, as well as the more challenging “Prestige” versions of those activities. Curse of Osiris raises the soft cap for Destiny 2 power levels to 330 from 300, which is the limit in vanilla Destiny 2. The recommended power level for the game’s toughest — and most rewarding — activities has also risen accordingly.