Why don't more people put Jeff Jarrett in the same category as Hogan and Nash as guys who caused WCW to fall?

Becasue he was an underrated wrestler.

Jarrett was hopping on the Titanic as it sank.  Sure, adding another body to the deck didn't help matters but the ship was already going down.  As for him taking a big money offer that he didn't deserve, well...everyone did that in WCW.  Midcard guys were getting paid better than some WWF main eventers after 'Sting Money' ceased to be the bar in which to aspire.  He didn't move the needle more in one direction or the other, he didn't bring in new fans or alienate Southerners who'd seen him grow up in Memphis. Did he have Russo's ear? Yeah, but putting the belt on Jarrett wasn't doing any more damage than Russo putting the belt on himself or Arquette.  Complaining about Jarrett's contribution to the downfall of WCW is like whining over a head cold when you have cancer.  The head cold might suck, but it isn't what's killing you.

I don't recall Jeff Jarrett ever having Creative Control or the ability to play Back Stage Politics to anywhere near the degree that Kevin Nash and Hulk Hogan did. Jeff Jarrett did not have a Favored Nations Clause in his Contract, I don't know that Jarrett's Contract would have been among the largest contracts in WCW? You know what Kevin Nash probably called Jeff Jarrett? Another Vanilla Midget. If you weren't at least 6'4 in his book you were probably a Midget.

Because the damage had already been done to WCW by the time he jumped. Think of it this way, if WCWs collapse was death by 1000 cuts, JJ joined at around 900 cuts