But it did establish the ridiculous precedent of the prime directive meaning 'We can't interfere with the deaths of millions', a precedent which created a good part of the series' biggest facepalm moments.
No, it didn't. That goes back to TOS. See A Private Little War.
In that episode, Kirk broke the non-interference directive only because the Klingons were already interfering.
That conference scene in Pen Pals
praised upthread took the debate going on in fan circles since TOS and upped the ante.