The word "canon" meant nothing to me back then. I did care about continuity; although I initially crammed every tie-in I had into my Trek timeline, I eventually realized that some of them had continuity problems or just weren't very good, and started picking and choosing which stories I counted as "real" and which ones I didn't. But I always thought of it as my own decision to make, based on my own judgment, and although I don't know for sure, I assume other fans at the time approached it the same way.
What I think the '89 Roddenberry memo and the Arnold approach to canon created was the perception in fandom that continuity was not something the individual decided on for oneself, but something that was imposed on them by a higher authority. I see so many people worrying about whether something is canon or not, acting as though someone had to give them permission to like a story. Even though the Roddenberry/Arnold approach stopped applying over two decades ago, there are still so many fans out there who assume it's still binding.