i am not understanding why you and a few others in here believe that.
solo players can do anything in D2 and do it successfully. I have completed the new raid 19 times with 19 different groups of players as a solo player (and failed another 5-6 times). The Bungie Destiny 2 app allows you to connect with randoms for any events you look for. Hell I was going to run the shattered throne/wish ender bow earlier today with randoms using the app but one clan mate (the last one that still plays but isn't a fan of raid - hasn't finished the new one) wanted to do with me and i randomly asked a few people on my friend list if they wanted to run it and someone said yes and we finished it.
Ther's nothing you can't do as a solo player. Just use the app to create or look for fireteams with what you want to play, raids, escalation protocol, worm, nightfall, farming for weapons.. it's all there for you.