I've heard people bash the first game for it's lack of a story and poorly designed enemies. The different enemy factions don't fight strikingly differently and the bosses all have similar attacks and a huge amount of health and I agree with them.
Despite all of that, I still enjoy the game. You're in a nearly post-apocalyptic universe, fighting cosmic forces that threaten all that is good and all that you love every single day. Day in and day out, you fight, die and live again thanks to the logic-defying power of the Light.
Your home and headquarters is the Tower in the last safe city. You venture to moons and planets terraformed centuries ago. You use rifles and bows (yes, you read that right) and cut down enemies with swords that need ammo (it's seriously fun, trust me).
You can engage your enemies in the open world, in Strikes, PvP matches, Gambit with your own fireteam or solo. If you're in the field you can encounter friends and allies that aid you in events or you aid in turning the tide of battle.
So what is Destiny 2? It's an adventure stricken with loss but "shot through with heroism and hope".
You might have to search up videos for the lore but aside from that, do play it because you have nothing to lose.
Sincerely,
A Titan of the Tower