I was actually the opposite to you, Jo. Fantasy was fine, but SF was a no-no. "Everyone" agreed when I was growing up that SF was all about ideas but the writing was terrible. Schools wouldn't put it on the curriculum! And school librarians often shunned it like the plague.

Fantasy was more respectable, perhaps because of Tolkien and Lewis who were Oxford dons, don'tyouknow…(said in posh voice…, but there really wasn't much of it being written for adults as I was growing up in the 50s.

For SF:

They allowed Animal Farm (1945) because it was an allegory, and 1984 (1949) because it hit at totalitarian regimes; Huxley because he was from a respectable, famous family and was an intellectual, (Brave New World 1932)…

Apart from the above exceptions, and "historical" writers like Verne and Wells, perhaps the first really pure SF book to hit my generation that was also "respected" by the traditional educational establishment, was Fahrenheit 451 (1953).

The greats of the period – Asimov, Heinlein etc were all ignored and heaven help you if you wanted to do a book report on any of their writing…

As a consequence, I too bought into this and believed what I was told, and therefore came late to the genre.