It is wild to try and trace how big of an impact Roger Corman had on Hollywood history

Without Corman, you don't get Hopper with the experience to make Easy Rider. Without Easy Rider the entire New Hollywood movement is hobbled, ESPECIALLY because without Corman you don't have Scorcese or Coppola so the crime film is now no longer a thing

You don't have James Cameron, so you don't get T2 which is the dawn of the modern event film. We also lose Titanic and Avatar both of which brought massive shifts of their own

You don't have Vincent Price as the face of horror for an entire decade. We lose Penelope Spheeris which means we lose the entire SNL movie canon, and probably Austin Powers.

We lose Ron Howard's lifelong career as a journeyman, as well as Jonathan Demme. We lose Joe Dante's career which means we maybe don't get the PG-13 for another few years after Gremlins

Without Coppola we lose Nic Cage. We lose Sophia Coppola. We probably lose the input the New Hollywood guys had on Star Wars, so that turns out to be a bomb

Not to mention the fact that Corman is practically the origin point of smuggling in social commentary into exploitation and genre films. The A-movies we have today are very much just an extrapolation of the b-movies he was making then