AO3 is probably your best bet for low-hassle, fandom-friendly story hosting. If you're not keen to learn HTML/CSS, you don't want to join me and hS on Neocities, though I think it's great. I can't recommend any of the older site-building platforms I used to know about. Tripod served me well for a long time, but it was never without issues, and I dunno if they've improved their visual site-builder since the last time I had anything to do with it. Maybe someone else can speak to something like Wordpress, which is fairly popular, but I haven't tried it myself.
So, tagging. As far as I've determined, there are two reasons to tag: 1) to help people find content they want to read, and 2) to warn them of things they might wish to avoid. The first is to your benefit if you want more people to find your story. The second is courteous. You don't have to do either of them. The bulk of your audience for PPC writing is here in the PPC community; you don't have to work that hard to drum up readers. You also don't have to bear the responsibility of thinking up everything that might hypothetically upset someone. The BIG things (graphic sex, graphic violence, any intersection of the two), sure, and AO3 has a special set of tags for those things that show up in bold text at the top of your tag cloud. Things you already know are sensitive for people around here, sure. Beyond that, though? The reader bears the ultimate responsibility for choosing either to risk seeing something upsetting to them or to stick to things with a G rating. That's life.
(For the record, this isn't anything I don't expect of myself. There are things I may choose to avoid in certain contexts or frames of mind, but one* is a totally normal and non-threatening aspect of life for many people, and the other** is a particular idiosyncrasy of mine. In neither case do I expect special consideration.)
So, while the enormous tag clouds on AO3 may be mind-boggling or intimidating (they put me off at first), I don't think they need to be. I think people just go way overboard with them, and also that they could be formatted better to be less bloody dense. Tag only as much as you want to, and know you can always add more later if you think of something you missed the first time. It's not a big deal.
* Alcohol. Especially irresponsible drinking being treated as no big deal. Daughter of an alcoholic here; I must sharply disagree that it's no big deal. That said, I've learned through exposure to deal with people drinking responsibly and to develop some curiosity about types of alcohol, how it's made, mixology, etc. I'll even taste things! It sure makes writing about it easier. Hence, no need for anyone to tiptoe around the subject generally.
** Bad things happening to cats. And, I mean, cruelty to animals and children and anything that can't contextualize its existence in general—but cats in particular. I've just always had a thing about cats. Like, there's this song from the perspective of a witch's familiar, and the witch is killed, and I cried the first time I heard it because the cat is left all alone. >.> It's weird. And it doesn't come up all that often, so I don't expect anyone to devote precious brain-space to remembering my weirdness.
Anyway, I take pride in being able to manage my stuff, even when confronted unexpectedly. That's not a boast or me looking down on anyone with a brain that doesn't work that way; just a thing that makes me feel good about myself.