"I suppose how I feel about John Wyndham is that it is very much like reading conventional literary fiction. He just changes one thing.... How would people react? What would they do? For all I know, all science fiction is like that, though."
Yes, well, a lot of good sci-fi is like that. There are surely some rubbish books just like there are in all genres, but the good ones take one idea and develop it really well.
I haven't read 'Triffids' but the idea of evil plants attacking people (without brains or muscles ffs
) sounds really silly and the sci-fi I like to read is the very clever stuff thoroughly thought out by very clever authors. In any case, if you think a book written in 1951 is the epitome of sci-fi, you probably need to read some more in this genre 