I don't believe that. In my adult life, my experience has been you can't get anyone to try something new based on word of mouth; its actually spoilers that is the thing that intrigues anyone enough to actually watch or play anything. And the angst of being "spoiled" is just someone confusing the sentiment of not being able to enjoy a first-time experience twice.
And then there is the problem of how almost all new systems are introduced through the story. Maybe they can, hypothetically, introduce a whole allied race without testing it, which might work out once, but that's the sort of thing that's only going to work out some of the time. Ion literally said "we didn't publicly test the last few bosses in Sepulcher, and people really enjoyed that." What? What is he basing that statement on? The reaction to new content within the fandom wasn't noticeably different. As for the cinematic, Raid groups in which I was in experiencing it live were either making fun of how bad it was or skipping it entirely. The only difference was the point in time in which the fandom was reacting: A later point in time, which seems no different than their business model of time-gating, which is a predatory business model when it comes to a subscription based service.
I don't think anyone prefers this new version of wow where all news comes directly from Ion's uncharismatic face.