The decline began when AW was given total control after DD was forced out and not replaced. Kroenke is not responsible for that but our then BoD and Chairman were as they were all the football equivalent of being 'gentlemen farmers', and ran this club like some hobby project.
The entire premise of our business structure with the BoD only administering the financial side of the business whilst the football operations looked after everything else (including generating the revenues), was out dated even before the PL era began. To date the only time we've acted like a BIG club was the decision to increase our match day gate and revenues, but even then we've managed to cock that up and gone backwards after a decade.
I recall a joke from a decade ago something akin to - How do you turn a potentially elite level football club into a mid-table team = give to AW and wait.
The sad part being that to put the club to rights we essentially need to strip away and replace everything AW did on and off the pitch for those 2 decades. Only his stats/records will remain and nothing of his football or approach to the game. He used to talk about giving back to the game and duty as a custodian, but nothing will remain from him.