First of all, I'm a huge Russo fan. And I stopped watching wrestling around the time he went to WCW so I haven't seen any of the stuff he did there and can't defend it.
I roll my eyes with the way people around here make fun of Vince. Before every pay-per-view, someone gets the hilarious idea to post a "book (insert ppv) russo style!" and all the same jokes are made. I gotta think people who don't respect what Russo did during his prime either don't understand TV or are too young to really appreciate the attitude era.
As we all know, since WWE bought their competition, they've been able to re-write history and Russo has got to be one of the biggest victims of this. Nobody gives him any credit. Certainly, not Vinny Mac and his family and rarely will you hear anything good from other wrestlers or crew about him. And it's bullshit.
If you want to know what Russo's job was, you should watch his youtube videos: https://www.youtube.com/watch?v=UxM1Y8c49xU If you want to know how to write good TV, watch his youtube videos.
Being a writer in TV is more than coming up with stories for everyone (which WWE doesn't do anymore) and more than making sure everyone has a character (which WWE doesn't do anymore). It's about making sure you have what Russo calls a "hook" and essentially that means starting your scenes before the beginning and leaving them before it's over. It's how you make things interesting, leaves viewers with questions and keep them coming back for more.
Another redditor said in this thread that the reason for the success of the Attitude Era was the sex, violence and outrageous storylines-- and that's true-- but more than that at the end of the RAW each week, you couldn't WAIT until next monday to see where the story was going. And that's something you'll see with every great TV show. Lost, Breaking Bad, etc. they all do this and Russo was a TV guy more than a wrestling guy (I think) and he was the best writer the wwe has ever had.
Another major thing that Russo did and doesn't get credit for, is his handling of the stars during that time. And not one of these motherfuckers give him any credit (but that's not uncommon for wrestlers or any movie or TV star to let their ego allow them to think they were helped by anyone else along the way.) So, Russo is juggling the ego of Steve Austin, and he's going to Steve and telling him ideas and Austin (paranoid over his own spot) is shooting down ideas and Russo is having to come up with something that works for Steve and works for lets say the Rock who is equally protective over his character! It's like doing a puzzle without have the picture to go off of AND doing that EVERY WEEK for THREE YEARS.
For a great example of what he was doing week in and week out, just blasting idea after idea towards talent. Just trying to spark something in them, check out this behind the scene clip with Mick Foley: https://www.youtube.com/watch?v=_Ax-eiYcJ60
And keep in mind this is just one actor he's working with out of a cast of like 40. It's utterly amazing.
Anyways, to answer your question, people hate Vince Russo because they simply don't understand what his job was.