In the US the execs trust the show runner to realise his vision; in the UK the execs interfere, so we mostly get shows 'aimed at a demographic' or intended to 'recreate a success'.
There are exceptions, such as the wonderful, Shadowline, but these seem to happen less and less often.
It is symptomatic of our country as a whole; independence of thought is mistrusted in our institutions and any challenge to the prevailing orthodoxy is dismissed as not being of the real world.