I am 100% with you. I think BC is one of the most overrated features ever on any console. I personally have very little if any use for it.
That said, I can see it being a nice seller for people who are new into the ecosystem. Me and you and most people on CAG have had consoles for generation after generation, so we've played all of the old games.
The other day though my brother told me he wanted to get an Xbox or PS5 for his kids for xmas and asked me which one to get. They haven't had any consoles ever. I told him it really depends what games they want to play and he said his kids mainly want to play sports games and then I said it doesn't really matter. But then he said he'd like to play some games too like COD and other games.
Then it hit me that BC would be great for him. So I then recommended he get a PS5 because there are so many awesome PS4 games that he will be able to play on it that he doesn't even know exist right now. TLOU2, God of War, Ghost of Tsushima, etc.