Yea this isn't true. People used guides just as much back then as they do now. The only difference is YouTube was not a thing. With how much was usually in stake (like a BCNM/KSNM orb from FFXI), people would look up every detail of the fight to make sure all their efforts don't go to waste. Actually if anything, people used guides even more back then. MMO's today at least give you a peace of mind to experiment before deciding to use a guide.
Yes, there where guides back then. But it was more, stand here for a bit of safety, or you can kite it around here. And also what moves it had. Now it's pretty much stand here for x seconds, then move here because boss use this move and then do this and that.

You can almost write a macro for your player and just play up that and go have a smoke while it do the fight for you.

There're actually less improvisation shows than scripted ones. In fact, I don't really see the former type being represented at all besides acting/theater teaching lessons.
You'll sometimes see a humorist being asked to react to something, throwing a few good jokes and call it a day, but you'll never see an unscripted opera or, like I said, a ballet... because it makes no sense.
Make it like this then. An actor might forget his lines. A good one can improvise it on spot and not stumble.