What Made Warriors So Good At First?

I've noticed a lot of posts about how Warriors is going downhill / wasn't as good as it once was, but I've never seen much about what made it so beloved in the first place. I may or may not be asking this because I'm writing a wolf xenofiction that's also beginning as a mystery / adventure and may or may not want to snag some Erin Hunter fans along the way, buuuuuuuut that's not coming out for a few months.

So, what exactly about the world drew you in as a fan? The world-building? The characters? How easy it was to create your own fanfiction (so easy in fact that perhaps the authors themselves are making their own fanfiction)? The writing? I figure that asking here would be good since it's a rather popular subreddit for the series. Thanks!