You can solo all of the main story quest except for 8-player boss battles and one required 24-player alliance raid series.
And that can be done through group finder and the wait is very short. However if you’re just into the story I’d recommend watching a YT video that cuts it together since the gameplay loop is really really boring
Shout-out to the Dan Floyd and his PlayFrame channel, where he’s been doing a condensed playthrough of the game with just the MSQ, the interesting side-content, and highly cut segments of the interim gameplay. It’s only near the end of Shadowbringers right now, but it’s what got me into the game (as someone who was never into and mostly still isn’t into MMOs).