I wasn't saying so, Mary, though I did want to question John's phrasing.
Dennis does a good job of puncturing the self-regard embodied in those late-60s experiences and habits of mind. He makes a successful (read: popular) poem of them, first of all, by latching onto the fact that nearly everyone of a certain age who had those experiences has asked "How did I change so much"? or "Was I really that silly?" The observations about the machismo and hypocrisy of the time are certainly right, but I'd say they're right out there on the poem's surface.
Some of the depths in "Summer of Love" are a little less attractive. For starters, he's parodying
"Recuerdo" by Edna St. Vincent Millay by aping its form, even down to the repetitions of "We were..." and the refrain-like opening lines of the stanzas. (He even reads it with exactly the same rhythm I've heard Millay use in a well-known recording.) I'd be willing to bet that--at least in America--his contemporary readers don't know the first thing about that poem, though they may have heard Millay's name. So why allude to her? I'd say his reason is to twit the literati. "Literary types" are the only ones who will get his point that Millay's famous self-indulgence is an archetype of the hippy-dippy approach.
Speaking of "hippy-dippy" let's look at "mighty Mississippi." This is one of those cases in which the search for a rhyme "drives" something with interesting effects. On the one hand, since the summer of love is connected unshakably to San Francisco, or Woodstock, or else to the whole country, "Mississippi" seems a little off. But "mighty Mississippi" is a phrase out of folk song and folk memory--which brings up the fact that the heyday of folk music was also still around, though fading, then. It's also a stock phrase, nearly a cliche, which begins to set us up to think about how stock-phrase-driven so much thinking was at the time.
I should be working now, so I'll stop there, but those two points seemed immediately clear to me.