As an ex fanboy (or fanboy lite) who has circled into hater section of recent, I can give you MY reasoning.

For starters theres the whole "we're not evil", and slowly becoming evil with obsessive data mining. But it's a huge company, so only strike 1.

They haven't released any useful innovation in my eyes, despite hoarding all the smartest people. Strike 2.

And the biggest strike to me is the significant decrease in product quality that I use. My google searches suck now, maps has become bloated with ads, and I don't even know what happened to messenger, but its pretty unusable for my friends and I that even the ones that work at google now text. Maybe a lot of this is the fault of companies aggressively marketing irrelevant things to get clicks, but to me, it's a platform problem. Strike 3, I'm a hater.

Again YMMV, but this is my reasoning.