Hehe, I'm an AO3 fan for real.
I got my fanfic "start" by reading Cats the Musical fics on Geocities and Angelfire sites... then transitioned to LJ and fanfiction.net; there's an HP fanfic I've been following there for ten years (that still updates!). This is when tropes like "The Official Fanfiction University of..." spinoffs were still popular
I got into AO3 in 2012 at the height of the Avengers fandom. And wow, what a site!! I was so impressed! The UI, the search functions, the fact that you could post explicit fic... incredible. TAGGING?! So cool!!
I look back on my AO3 boomarks and can easily identify slices of my life: college me was very into Marvel and Teen Wolf (MTV), then I had a Merlin phase, the summer I went to London I was very into 00Q, then One Direction, then anime... yeah. I love fanfic.
I write as well; mostly explicit oneshots - I'm not as confident in my writing as I want to be (and I don't think I have the attention span) to complete a novel of any significant size. I finished my first multichap fic in March (only 3 chapters, 11k, it BARELY counts), and it was pretty significant for me.
I love those massive epics of fic... there's always one in every fandom, ya know? lol. It's always interesting for me to watch how certain fanons from popular fics will make their way into the wider fanon and show up in art from BNFs, etc.
Then I also like the offbeat, explicit fics too. Chances are if you're horny for what you're writing, your enthusiasm will shine through, and it'll be awesome.
To your point about what you said about fanfic shaping your daily life: I attribute my communication skills to fanfic. I joke about how I've seen enough fic based off of misunderstandings that it taught me how to talk to people, but it's kind of true!