I would never refer to ECW as a whole as garbage, but they produced a lot more garbage than they did golden nuggets. They deserve a lot of credit for introducing different concepts to their fans, and being a Jack of all trades. That being said the brutal violence is what brought the fans to the arena, it was just a coincidence that some of those fans were also open-minded to other outlets of wrestling.
Sabu deserves a little bit more credit than just being called a "flipping New Jack" as he could work more than just the garbage wrestling style where as New Jack couldn't even properly execute a fucking wrist lock. New Jack only got monster pops when he was stapling people's faces or diving off of balconies. Sabu was able to work just about any style but primarily worked the garbage style because that's what got him the most over in that environment.
ECW obviously wasn't complete garbage or people wouldn't still be clamoring about it all these years later. Is it overrated? Definitely. But it still can't be denied that it provided a major change in the landscape of pro wrestling and was the precursor to the Attitude era.