It's the money aspect, which as @HalfTimeSayers says rightly mentions heavily influences R&D, the technology in the cars, resources of the teams and reliability.Turning your point on it's head, is there another motor sport that suffers from this issue. MotoGP, WRC, BTCC, Indycar all have multiple exciting events were consistently F1 it seems to be the exception.
The cars have ridiculous levels of aerodynamics and grip and which, while making it faster and safer, have produced vehicles that are difficult to overtake.
You then get situations now where one team is way ahead of the rest. I love F1, but you can understand why so many people struggle to gain interest.