@9hans.fritz6I think part of the reason is that there was this opaqueness about the inner workings of "Eastern" entertainment industry pre-2000ish, whereas everyone knows how Hollywood worked that leaves very little to imagination (from Hays code and censorship machine to the influence of unions). So you could reasonably write a story about going back to, say, working with Bruce Lee in early 1970s Hong Kong, but it would be laughably out of place for for late 1960s Hollywood.
I feel the only sensible entry point, unless you start with a character already inside the Hollywood machine, is the record labels. But I don't think they would make good stories for the readers. For example, you go back as Dick Rowe (or someone close to him) and not reject the Beatles (twice!); but now British Decca did not have sufficient ties in the US that would make them the smashing hits in 1964 tour, and worse, has to split limited resources between the Beatles and the Rolling Stones (because of course you have to sign the RS as well, whereas in our timeline Decca signed RS as a result of rejecting B), angering both sets of fans. Most likely, you will be writing some variants of the payola/pay-to-play scandals again, and that is boring.