Destiny 2 is described as 'Humanity's last safe city has fallen to an overwhelming invasion force, led by Ghaul, the imposing commander of the brutal Red Legion. He has stripped the city's Guardians of their power, and forced the survivors to flee' and is a first-person shooter in the games category. There are more than 10 games similar to Destiny 2 for a variety of platforms, including Windows, Xbox, Playstation, Steam and Mac apps. The best Destiny 2 alternative is Fallout. It's not free, so if you're looking for a free alternative, you could try Warframe or Tesseract (game). Other Destiny 2 like games are Doom, Borderlands, BioShock and Prodeus.
It is simply a shooter, and has no real loot/rpg elements.