The Destiny 2 beta answers some mechanical questions. Certainly if you’re a PvP player then finding out how 4v4 matches work or what the new weapon structure feels like matters alot. For PvE, we don’t see much more than we’ve seen from previous Destiny content. The Taken King and Rise of Iron made an effort to involve more direct story and dialogue in missions, and there’s a clear lineage in Homecoming from what they were doing earlier (with the notable addition of characters actually showing up in the mission instead of just talking in your ear).
Maybe your best clue to what the world of Destiny 2 will feel like is to look at how they experimented with progression and side content in the previous D1 expansions. The Dreadnaught was full of hidden chambers and chests that required puzzle solving to unlock, and there were alternative mission paths and hidden quests that unlocked unique gear. Rise of Iron’s post-story solo content was structured around repeatable weekly quests with rotating unlocks that gave you a reason to come back each week. I’d be willing to bet they used these expansions to test and refine their concepts for the Destiny 2 open world and endgame progression.
e: If I had to guess why there’s no patrol in the beta this time around, I’d say it’s because they’ve actually got content in the open world that they don’t want to reveal yet, and there’s no way to block access to it while letting you explore the environment. People on reddit have already found a public event and glitched into a lost sector just from the Nessus strike.