Too Long; Didn't Read
One of the most reliable ways to discern whether a corporation has begun to rot is to gauge the derivative of the utility its products provide over time. A company like Apple witnessed a huge spike in average product utility when they released the iPhone, which increased for some time, but eventually plateaued when they started removing vital phone functions like the 3.5mm jack. Generally speaking, most companies experience either an S-curve or a parabolic curve of this kind of utility: the former types generally find their niche, fill it, and operate in comfortable profit without innovating much more; the latter types manage to muck things up and crash and burn having failed to understand their product.