They lost me a looong time ago.... After having to grind new max level gear and upgrade my old guns for their third time because they keep raising the damn cap with every expansion.
Quit during house of wolves. The fact they didn't have a raid and that the were yet again forcing me to upgrade all my gear made me realise what I was doing was pointless, that no matter how much effort I would put to reach max level and gear up properly, it was all for nothing since the minute the the next expansion would drop, it was going to render all my player progression meaningless instantly.
I actually felt a huge relief not to constantly have to log into the game to do my weekly grinds and raids on all three characters, which made me realise I wasn't really having fun in the first place. I gladly skilpped taken king and the last expansion too.. I mean, I figured "hey, why bother, it's all going to be rendered useless when Destiny 2 gets out".
When Destiny 2 was announced, I though for a second about going back. I was expecting a new game building up on Destiny 1's foundation, not a game that basically would destroy all existing player progression, dump all existing content in the garbage can and and start from scratch. The fact that all the gameplay vids I've seen look exactly like Destiny 1 doesn't help either... They threw everything away to rebuild the exact same thing and sell you the same experience again.
I'm just glad I move to warframe instead. Here I get to keep all my 33 maxed level frames, all my maxed guns, when there's new content added, it's added on top of the existing content, not replacing or deleting existing stuff. It's building and improving it's foundation, it's core gameplay without constantly throwing player progression down the crapper because "hey, new level cap means you must throw all your old stuff away" garbage. Wish more game devs would respect the time invested by their players into their game, and reward vets instead of constantly forcing them to re-earn ther vet status.