Objectively I think everyone can acknowledge shoe technology exists on a continuum.
At one end you have those trail sandals that some ultra runners insist on wearing that are basically just a thin piece of leather for protection.
A the other end, if you even call them shoes, would be something like this:
https://www.youtube.com/watch?v=Kc97wsBcf-8
that no-one wants to see runners using. Both are passive, with no external energy sources, and neither involve wheels or other technologies that are categorically different from the essential running process of moving forward by planting one foot after the other.
I've been running 22 years and have worn hundreds of pairs of shoes with dozens of patented technologies. I've run in shoes with plates (Mizuno, and many trail shoes with rock plates), air pockets (Reebok Hexalite, Nike Air), gel pockets (Asics, Nike), shoes with different foams and different densities of the same foam but it always, always felt like the different models were playing in the same sandpit. And most runners responded to the available choices in the same way - heavier more cushioned shoes for training, lighter, smaller less structured flats for racing.
The Fly line is a transformational change even if it's hard to draw a bright line or pin down exactly what should or should not be allowed. I've run in the Zoom Flys, the Zoom Fly SPs, the Zoom Fly Flyknit and the 4%s. I've gone from racing in a NB flat with a stack height of under 10mm to rolling round on foam pillows with a stack height of over 40mm. The heel stack on the alpha flys is reportedly 51mm. I'm faster, my teammates and competitors are faster, the pros are faster. Unless you have weird feet, you're running in these shoes or you're not really trying.
I would be in favor of the authorities stepping in and regulating RACING shoe design now, before 50mm becomes 70mm becomes 90mm. To be clear, you can leave people to train in whatever they want but regulate what they can show up and race in. Two obvious starts at rules could be:
- maximum stack height; and
- maximum of one midsole material (excluding different densities of the same material in the case of foam)