What now?

Started playing the game for the first time a few days ago and just finished ending E

Im unsatisfied, to say the least (not that it was bad, this is clearly the point)

And I just...what do I do now?

There's content I didn't get through, I didn't really engage with side quests, but is there anything else that will give me the hit of catharsis I was expecting? Anything that will satisfy my fixation on this game and make my brain feel like the investment in the fixation was worth it?

Please help, it's bumming me out