An ideology is like a description of what is wrong with the world, and a prescription to make improvements. Many ideologies also speak to an optimistic, idealistic hope for betterment, or at least, a situation where troubles melt like lemon drops.
Of course, happy little bluebirds can fly beyond the rainbow, but in practice we are often left with making do with the status quo. Likewise, many an idealistic ideology promising that the dreams you dream will come true, fail to deliver upon attempts at implementation.
Judy Garland sang this Harold Arlen and lyrics by E.Y. Harburg classic for the 1939 film, The Wizard of Oz – as if that needs mentioning. Many others have covered the song, most notably in recent years, Israel Kamakawiwoʻole: