There used to be an "anything goes" series… the original Can-Am (1966-1986) - what Car and Driver called "the vehicular equivalent of great white sharks in a goldfish bowl". The regulations were basically "two seats, enclosed fenders". There was effectively no regulation of engine size or configuration, or of aerodynamics. It was abandoned in part due to extreme cost, and in part due to the safety problems.
The last straw for Can-Am, really, was Porsche simply pouring money into it with the 917 until no one could compete with them, rendering the racing kind of boring. Tight regulation in F1 and other racing forms keeps the focus on the driver, not the car.
Safety problems, indeed. The 917/30, f'rinstance, had a chassis and bodywork you'd be leery of building into a child's pedal car wrapped around a twin-turbo flat twelve that could deliver 1800 bhp when turned up to eleven (and, given the turbos of the time, that power was pretty much on/off rather than something you could lay on gradually). But those were the days when "retirement" and "race car driver" were practically mutually exclusive terms.
Tight regulation in F1 and other racing forms keeps the focus on the driver, not the car.
F1 has always been about the car, and the most heralded of driver in one car often becomes completely humdrum in another, and vice versa. Tight regulations simply change the parameters that the car makers have to optimize, and ultimately came about because without continually restricting the engineering, the cars were becoming impossibly fast.
The only series that are really about the driver have identical cars. I believe that is how the Formula E thing is planned, for instance, at least to begin.
The last straw for Can-Am, really, was Porsche simply pouring money into it with the 917 until no one could compete with them, rendering the racing kind of boring. Tight regulation in F1 and other racing forms keeps the focus on the driver, not the car.