Exuberant? We are in an economic recovery and things have been slowly getting better, but I'd hardly call these times exuberant.
Your comparison would make more sense if the themed or film entertainment industry were as new as the mobile phone industry. Theme parks are over 50 years old, the film industry is over 100 years old. Disney started when films were beginning to emerge, they managed to make it through what was surely a tumultuous time - the birth of a completely new product. Cell phones went from nonexistent to in the hands of almost every man, woman, and child in what? around 15 years? Is it surprising that some companies rocketed to success in the beginning and then lost market share to other companies (Apple) who took it farther and did a better job? Themed entertainment is hardly in its infancy, so rocketing to success by selling a brand new product in the very early stages doesn't apply to the Disney parks now, maybe in 1960?
We know a few things - Disney is spending money on WDW, there are construction walls up in AK and MK, and they just completed a large expansion of Fantasyland while implementing a very expensive new system, MM+. People may complain about these improvements and their timelines, but Disney is actively doing things/spending money to enhance guest experiences/help with crowds, such as the hub construction and re-theming of the backstage overflow path in MK.
They are also increasing shareholder dividends. To me, these actions do not spell out the doom and gloom of a company in demise.