I'm kind of less focused on the whole exotic/random quest things and more into trying to complete each expansion campaign quest chain(s) first to see the world/lore. And there seems to be quite a bit especially not knowing where to go instantly while exploring and the overall "charm" of the UX being terribly unhelpful so I am not breezing through it.
I don't particularly care about/get excited about loot outside of getting what I need to complete content in any game so that type of stuff is low prio atm.
The exotic chains can add a MASSIVE amount of lore. Lament (exotic sword on Europa) is one of the biggest reveals of NPC backstory I've seen. I don't know that the Xeno or Deathbringer questlines have a ton of extra lore, but there is a lot of extra in the story line that can be added.
Also, when Lenas talks about "endgame" it's more like "late game" and then you get into actual endgame.
Late-game being raids, Nightfalls, and PVP.
End game being Master Raid, Grand Master Nightfall, Trials, and Ranked PVP.
Do you need godrolls/exotics for endgame or late-game: No, but it helps. I know that I there are "godroll perks" that I just personally don't like. I'm not great at getting kills in PVP, so I stay away from the kill-perks and focus on other perks to enhance damage or utility (I love frenzy, can't use multi-kill clip in PVP). This is what others have been talking about, you'll find perks you like and use those.
Also, with DIM or other tools you can find some of the better loot piece combinations and create a build with multiple 100 stat builds (hard-cap on stat values, any over 100 don't increase effectiveness).