Bungie has taken Destiny 2 servers offline to perform some maintenance. Lately Bungie has put a lot of hours into maintaining the servers but this time the are offline all day.
Destiny 2 is very popular with the free to play model. The game does have modern system requirements so a potato is not going to be very successful.
More Steam members are several games so playing something else is all I can suggest. I play Alien Swarm: Reactive Drop which is free to play. Beware while Source engine based, the game is tricky to play. Some of my friends have over 2000 hours into playing it, while I have about 260 hours into it so far.
Destiny 2 should be back to normal Friday.