As far as the collaborative medium aspect, we have a tendency to want to believe in auteur theory, which is why Gene got all the credit for Trek, and prior to the prequels, Lucas got all the accolades for Star Wars. It's only later is it better understood that what we saw was the combined influence of many creative forces, sometimes working in sync, and sometimes in fierce opposition, leading to some sort of compromise. Back in the 60s I can only think of one television writer who was known for having his scripts delivered straight through, and that's Rod Serling, since TZ was built around him, but even he had his share of nasty fights with the execs, at least by the time you get to Night Gallery.
What to the people who made these things might have seemed like a tragic capitulation might to the audience appear as a great piece of entertainment. But if you want to align yourself with one particular strong personality with an axe to grind (and Ellison is certainly known for both) then it's easy to take sides, when in effect, it's a very gray area.
There is also the issue of authorship. Someone known for writing novels is not going to be used to the rewrite process, but there isn't the same purity in screenwriting. I don't know how it was then, but these days it's uncommon for anything to have a single writer attached to it, especially big box-office movies. Even take someone like Christopher Nolan. He works with his brother on scripts. Usually the collaboration makes for a stronger story. You need a strong devil's advocate by your side to challenge all your ideas.