you can blame IAAF for not clearly defining what shoe is legal or not, or whether they or not enforce their rulings. IAAF says they allow shoes because they protect you feet, then springs should be allowed because they are a form of cushioning. one can also argue that every outsole of a shoe is a spring. there is also the rabbit hole of track spikes or starting blocks giving us "unfair advantage"
imo, 2 rules need to be put in place
1) a maximum stack height of the shoe (maybe 1.5 inches? 2 inches?)
2) the shoe cannot use any electricity
everything else is fair game imo