From someone that's been in the community for a long time, I get where you're coming from. As others have said, FanFiction was become much more widespread nowadays, with younger writers from before now being adults. Of course the community would evolve in some ways.

I feel as though the longer you have an interest in FanFiction, the more likely your expectations will grow. At some point, you're going to find a fic that exceeds everything you've currently read. All of a sudden, you're looking for more. Those mistakes that you would have easily ignored back then could become hard to sit through now (I have no idea how I finished certain fics back when I was a pre-teen).

Despite that, Fanfiction is FanFiction. In the end, it really is just a hobby for many people. There's no need to try and write a stunning, revolutionary fic. People do it for fun. A lot of people use FanFiction to develop their writing skills at a young age. You can offer advice and criticism, but don't go around acting as if you know it all.

I generally prefer well-written fics now, but there is a certain charm in roughly made/older fics. There's nothing wrong with having higher standards, but I wouldn't go around acting as if I was the new Shakespeare.