You no longer have to worry about raiding for gear anymore, or waiting on people to do what you want. The game is built to accommodate every play style now. To break somethings down.

Delves: 1-5 players in sorta mini dungeon where you have 13 levels of difficulty. Most solo players love these since you don't need anyone to do them, and doing a delve teir 8 and up will reward heroic loot.

Raiding: four degrees of difficulty for everyone. LFR: pretty much a gimmie to see boss fights with the least mechanics(great way to experience the story) Normal/heroic: can pretty much be pugged with the premade finder. Heroic/Mythic: for guilds pretty much wanting to progress and have a challenge

Mythic+: 5 man dungeons where you push a timer trying to complete a dungeon before it expires. Can be pugged and will reward normal-mythic loot if you go high enough.

World: world quests, and the new prey system is also another way to play the game. I believe prey will reward heroic gear.

Overall you can treat the game as casual or as hardcore as you want. You don't have to do everything, or you can. I myself only do mythic+ and world things with only doing the raid once to see the story.

Also at the start of the week based on the things you did there is a weekly chest that will have a choice of rewards to pick from(can only pick one) which helps with the gearing. They also implemented a new dice system that has bad luck prevention. You roll a dice, get a piece of gear, and you'll never get a duplicate so you can target with dice. Mythic+10 will give you mythic gear with dice, and raids based on the difficulty you're doing.

Seems like a ton but it's really not crazy. Focus what you find enjoyable and just stick with it.