You can't go into Age of Triumph with the mind set of "but my progress and items won't carry over in Destiny 2 so why should I grind?" Because none of your Call of Duty, Halo or Gears of War stats from previous games carry over into future games. It's just how video games are. If you think like that then you're missing out on a fun experience and essentially you'd never buy any new games. You just play and grind and then when a new one comes out you play and grind in that one. It's just how it goes.
EDIT: So because everyone and their mother likes to throw around the bullshit excuse of oh Bungie said our characters and all the loot we have earned will travel with us, I decided to do some research. In no article or any interview did they say loot you acquire will come with you. Here is a quote from Christopher Barret (a creative director) that he gave fo GamesRadar over the summer of 2016 a few months before Rise of Iron came out: Will Destiny year nine be recognisable to year two players? “I hope it’s coherent. We want it to be,” was Barretts answer “We have some ideas where we want the world to go. But I think we’d be kidding ourselves if we knew what exactly what was going to happen nine years from now”.
That 10 year plan literally just means they're over the course of 10 years they're trying to establish the Destiny world as a new big franchise.
Futhermore let's do more research. Oh look an article in December 2014 by The Guardian. In this interview Jonty Barnes (head of production) said “So what I’ll say to you is: we said that we were a ten-year game, and both Activision and Bungie have committed to being wholly behind the large effort, and it’s a large investment for both sides. I don’t think there’s any set date – ten years is just representing the go-forward presence and the way that we think about doing things.”
Now okay there is that article from IGN that says player progression will carry over, but come the fuck on it's IGN ffs, they lie, they're not reliable, they're inaccurate. If you believe anything IGN says in terms of news and even game reviews, then I feel bad for you.