I know there's a perception that Leonard Maizlish was the power behind the throne, but even if he was meddling with the production and causing general mayhem, he was still there at Roddenberry's behest, especially in the first season.
You may have a point about Roddenberry spiking Gerrold's story for personal reasons. Star Trek was never the sole creation of Gene Roddenberry. Justman, Solow, Coon, Fontana and others arguably added as much to the franchise as Roddenberry as he himself did (though I don't dispute his was the most pivotal contribution). But one gets the sense he wasn't willing to be as collaborative during TNG as he had been during TOS.
It's a shame Gerrold left under such bad circumstances. There's a lof of his DNA in TNG. Some of the ideas - like the Captain not leaving the ship to go on landing parties (err, sorry, away missions) - came straight out of his book The World of Star Trek.