Do you like the content you had in the base game? Do you like endgame you had until Tuesday? Did you purchase Curse of Osiris, no? Well too bad, you don't get to play the Destiny 2 endgame you previously paid for. It is locked until you pay Bungie's toll. I mean, buy the expansion.
After gains, Bungie are now taking away your content. If you paid full price for the game, you may expect being able to play what you paid for. Well, the endgame you had access to before Curse of Osiris launch is no longer available to you. Just like that.
When an expansion lands in any game, it is to be expected that the level cap will get raised, it's just business as usual. What you don't expect is that power requirements to enter endgame activities will lock you out of them. Since the expansion hit live servers, both power and character level caps go increased as well as requirements for endgame activities. In vanilla game you could play Prestige versions of Nightfall strike and the raid with power level of 300, which was increased to 330 with Curse of Osiris. Now, if you don't have the expansion, the maximum power you can reach is 305 and you can no longer play those activities.
Curse of Osiris also reintroduced heroic strike playlists that let you join a random strike from either base game or the expansion. Power requirement isn't that high, standing at 270, but it's also unavailable unless you purchase the expansion.
Veteran Destiny players could potentially see this coming, as Bungie pulled the rug out from under their feet before, with The Dark Below expansion for the original Destiny, in September 2014, where they did pretty much the same.
This development hit the PC players even harder, as Destiny 2 released almost seven weeks later than it did on consoles and therefore the PC playerbase had that much less time to go through the base game, and by extent less time to experience the endgame.
Just over a week ago, when the hidden XP scaling mechanic was the talk of the town, Bungie promised transparency and they delivered with Curse of Osiris. You either pay up to play what you already paid for or you don't get to play it. Plain as day.