Well, there is a difference between monologue/lecture and conversation. I suppose Keats thought that since he hadn't bought a ticket and he was with Wordsworth at his home, he was going to participate in a *conversation* where *both* people speak for a similar amount of time and share ideas

Wordsworth really should have put a sign out front for Keats to read before he walked in the door: "Wordsworth Lecture Today. Open your mouth and my wife/bouncer will see you to the door!"
In all seriousness, of course it would be wonderful to hear smart people speak. . .but some of the glitter rubs off when the talker is in obvious love with himself to the point he doesn't think anyone else's ideas are worth a grain of salt. No one is so smart or wise that he couldn't benefit from another opinion.