I'm afraid that's not only in Science Fiction but every Medium from Popular written Fiction, Art, Cinema...The quality of writing these days is all too often rather slipshod, and that's become much too acceptable. Poor sentence construction, poor use of simile, poorly used vocabulary, strained metaphor... it's all quite rife in far too much writing, and readers quite often defend this as good writing. It's not. It's at best mediocre.
I'm not sure that Television was any good to begin with, the cinema which is now in it's worst decade since the 1930's
Art though has had the greatest fall. 400 odd years since Michaelangelo sculpted 'David', what passes for Art today is used condoms on a bed, Skeletons in cage and a horses head in an air-tight clear plastic Box with flies buzzing around it