I played D1 and imported my characters to D2 at launch and went through the whole losing the light to the Cabal dude and finding it again with new supers.
Then I stopped playing after Forsaken and returned at the end of the season of the Deep.
I recently deleted 2 of my chars (I had 3 Warlocks, in D1 it was advantageous because class exotics where really hard to get, not like now that you get showered with exotics every week) and made a Titan and a Hunter.
I started with the Titan and got a slideshow quickly resuming everything and start in the Cosmodrome just like D1.
Did they erase the whole losing the light and the Cabal invasion of the Tower, and merged D1 with D2?