I quite enjoyed reading Enid Blyton in the 1960s, although my children weren't keen on them in the late 1980s. Perhaps they had already become dated by then. The publisher Hodder is reissuing the Famous Five series with changes made to the language, as their market research showed that the old-fashioned expressions in the books put children off. Expressions such as 'lashings of ginger beer', 'I say', 'jolly nice' and 'mercy me' will disappear.
This story has been in the news recently (eg here) but Blyton's books have been edited periodically over the decades. Racist storylines and language have been removed, names have been changed (eg Bessie became Beth and Fanny became Frannie), and words that have changed in meaning since Blyton wrote them, such as 'gay' and 'queer', have been replaced. That reminds me; Hodder intends to replace the word 'peculiar' with 'strange', which presumably means that the word 'peculiar' must be becoming old-fashioned.
Hodder says that there will be no changes to the storylines, but the life and the adventures of the Famous Five bear as little relation to children's lives today as their language does. Blyton's Five had plenty of jolly japes -- exploring caves, chasing thieves, catching smugglers, camping, cycling -- and all without any adults being around.