When Jean Todt stated in his manifesto for a second term of FIA presidency that he wanted a MotoGP-style ladder of single-seater racing at Formula 1 events, he changed the course of junior motorsport in Europe.
Back then, in 2013, there was a neat equilibrium. GP2 and GP3 supported F1, the FIA Formula 3 European Championship ran with the DTM as a parallel series to GP3, both feeding into GP2. Renault had its successful Formula Renault 3.5 category, plus its FR 2.0 pyramid of Eurocup, ALPS and Northern European Cup, and this group of Renault championships in turn also fed drivers into F1.
There were some renegade series, but these generally had the less-well-financed drivers and weren't really taking drivers away from the major categories.