I’d question the underlying assumption of your question - were indie films more thriving in the 70s compared to today? Indie films today are certainly thriving - there are more of them than ever, distributors such as A24 make them widely known and they also grow organically online as well. Most cities have small film festivals that indie films make the circuits in. Oscars are now being won by indie films instead of blockbusters. That doesn’t mean they are profitable though which was the topic of the OP. I don’t think indie films were particularly profitable in the 70s either though?
I’d question the underlying assumption of your question - were indie films more thriving in the 70s compared to today? Indie films today are certainly thriving - there are more of them than ever, distributors such as A24 make them widely known and they also grow organically online as well. Most cities have small film festivals that indie films make the circuits in. Oscars are now being won by indie films instead of blockbusters. That doesn’t mean they are profitable though which was the topic of the OP. I don’t think indie films were particularly profitable in the 70s either though?