I started it back in Form 1 so 2017. I caught up near the beginning of Wano. I had wanted to start it for a while but after a friend started talking about it, I started seriously looking for it to watch.
As for why it's still one of my favourites, I like the characters and the world Oda created. I'm interested in a lot of the mysteries but I'd say the characters I like are what keep me reading whether it's Sanji, Ace, Corazon, Marco, Drake or most of the Straw Hats really. Plus even though I have issues with it, I find myself enjoying it when I read/watch it.
Revolutionaries seem like a faction I'd like since they're actively liberating people from the control and influence of the World Government. Pirates are cool but I'm not sure I'd be all that into finding the One Piece and the Marines have plenty of great people but I'd rather not be affiliated/connected to the World Government.